1. What is PL/SQL ?
Ans. PL/SQL is a procedural language that has both interactive SQL and procedural programming language constructs such as iteration, conditional branching.
3. What are the components of a PL/SQL block ?
Ans. A set of related declarations and procedural statements is called block.
4. What are the components of a PL/SQL Block ?
Ans. Declarative part, Executable part and Exception part.
Datatypes PL/SQL
5. What are the datatypes a available in PL/SQL ?
Ans. Some scalar data types such as NUMBER, VARCHAR2, DATE, CHAR, LONG, BOOLEAN.
Some composite data types such as RECORD & TABLE.
6. What are % TYPE and % ROWTYPE ? What are the advantages of using these over datatypes?
Ans. % TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are : I. Need not know about variable’s data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.
7. What is difference between % ROWTYPE and TYPE RECORD ?
Ans. % ROWTYPE is to be used whenever query returns a entire row of a table or view.
TYPE rec RECORD is to be used whenever query returns columns of different
table or views and variables.
E.g. TYPE r_emp is RECORD (eno emp.empno% type,ename emp ename %type
);
e_rec emp% ROWTYPE
cursor c1 is select empno,deptno from emp;
e_rec c1 %ROWTYPE.
8. What is PL/SQL table ?
Ans. Objects of type TABLE are called “PL/SQL tables”, which are modeled as (but not the same as) database tables, PL/SQL tables use a primary PL/SQL tables can have one column and a primary key.
9. What is a cursor ? Why Cursor is required ?
Ans. Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.
10. Explain the two type of Cursors ?
There are two types of cursors, Implicit Cursor and Explicit Cursor.
PL/SQL uses Implicit Cursors for queries.
User defined cursors are called Explicit Cursors. They can be declared and used.
11. What are the PL/SQL Statements used in cursor processing ?
Ans. DECLARE CURSOR cursor name, OPEN cursor name, FETCH cursor name INTO or Record types, CLOSE cursor name.
12. What are the cursor attributes used in PL/SQL ?
Ans. %ISOPEN – to check whether cursor is open or not
% ROWCOUNT – number of rows fetched/updated/deleted.
% FOUND – to check whether cursor has fetched any row. True if rows are fetched.
% NOT FOUND – to check whether cursor has fetched any row. True if no rows are fetched.
These attributes are proceeded with SQL for Implicit Cursors and with Cursor name for Explicit Cursors.
13. What is a cursor for loop ?
Ans. Cursor for loop implicitly declares %ROWTYPE as loop index, opens a cursor, fetches rows of values from active set into fields in the record and closes
when all the records have been processed.
eg. FOR emp_rec IN C1 LOOP
salary_total := salary_total +emp_rec sal;
END LOOP;
14. What will happen after commit statement ?
Ans. Cursor C1 is
Select empno,
ename from emp;
Begin
open C1; loop
Fetch C1 into
eno.ename;
Exit When
C1 %notfound;—–
commit;
end loop;
end; The cursor having query as SELECT …. FOR UPDATE gets closed after COMMIT/ROLLBACK.
The cursor having query as SELECT…. does not get closed even after COMMIT/ROLLBACK.
15. Explain the usage of WHERE CURRENT OF clause in cursors ?
Ans. WHERE CURRENT OF clause in an UPDATE, DELETE statement refers to the latest row fetched from a cursor.
16. What is a database trigger ? Name some usages of database trigger ?
Ans. Database trigger is stored PL/SQL program unit associated with a specific database table. Usages are Audit data modifications, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.
17. How many types of database triggers can be specified on a table ? What are they ?
Ans. Insert Update Delete
Before Row o.k. o.k. o.k.
After Row o.k. o.k. o.k.
Before Statement o.k. o.k. o.k.
After Statement o.k. o.k. o.k.
If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.
If WHEN clause is specified, the trigger fires according to the returned boolean value.
18. Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger ? Why ?
Ans.It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing.
19. What are two virtual tables available during database trigger execution ?
Ans. The table columns are referred as OLD.column_name and NEW.column_name.
For triggers related to INSERT only NEW.column_name values only available.
For triggers related to UPDATE only OLD.column_name NEW.column_name values only available.
For triggers related to DELETE only OLD.column_name values only available.
20. What happens if a procedure that updates a column of table X is called in a database trigger of the same table ?
Ans. Mutation of table occurs.
21. What is an Exception ? What are types of Exception ?
Ans. Exception is the error handling part of PL/SQL block. The types are Predefined and user_defined. Some of Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
22. What is Pragma EXECPTION_INIT ? Explain the usage ?
Ans. The PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. To get an error message of a specific oracle error.
e.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number)
23. What is Raise_application_error ?
Ans. Raise_application_error is a procedure of package DBMS_STANDARD which allows to issue an user_defined error messages from stored sub-program or database trigger.
24. What are the return values of functions SQLCODE and SQLERRM ?
Ans. SQLCODE returns the latest code of the error that has occurred.
SQLERRM returns the relevant error message of the SQLCODE.
25. Where the Pre_defined_exceptions are stored ?
Ans. In the standard package.
26. What is a stored procedure ?
Ans. A stored procedure is a sequence of statements that perform specific function.
27. What is difference between a PROCEDURE & FUNCTION ?
Ans. A FUNCTION always returns a value using the return statement.
A PROCEDURE may return one or more values through parameters or may not return at all.
28. What are advantages fo Stored Procedures ?
Ans. Extensibility, Modularity, Reusability, Maintainability and one time compilation.
29. What are the modes of parameters that can be passed to a procedure ?
Ans. IN, OUT, IN-OUT parameters.
30. What are the two parts of a procedure ?
Ans. Procedure Specification and Procedure Body.
31. Give the structure of the procedure ?
Ans. PROCEDURE name (parameter list…..)
is
local variable declarations
BEGIN
Executable statements.
Exception.
exception handlers
end;
32. Give the structure of the function ?
Ans. FUNCTION name (argument list …..) Return datatype is
local variable declarations
Begin
executable statements
Exception
execution handlers
End;
33. Explain how procedures and functions are called in a PL/SQL block ?
Ans. Function is called as part of an expression.
sal := calculate_sal (‘a822′);
procedure is called as a PL/SQL statement
calculate_bonus (‘A822′);
34. What is Overloading of procedures ?
Ans. The Same procedure name is repeated with parameters of different datatypes and parameters in different positions, varying number of parameters is called overloading of procedures.
e.g. DBMS_OUTPUT put_line
35. What is a package ? What are the advantages of packages ?
Ans. Package is a database object that groups logically related procedures.
The advantages of packages are Modularity, Easier Application Design, Information. Hiding,. reusability and Better Performance.
36.What are two parts of package ?
Ans. The two parts of package are PACKAGE SPECIFICATION & PACKAGE BODY.
Package Specification contains declarations that are global to the packages and local to the schema.
Package Body contains actual procedures and local declaration of the procedures and cursor declarations.
37. What is difference between a Cursor declared in a procedure and Cursor declared in a package specification ?
Ans. A cursor declared in a package specification is global and can be accessed by other procedures or procedures in a package.
A cursor declared in a procedure is local to the procedure that can not be accessed by other procedures.
38. Name the tables where characteristics of Package, procedure and functions are stored ?
Ans. User_objects, User_Source and User_error .....
PL/SQL interview qiuestions:-
1. Which of the following statements is true about implicit cursors?
1. Implicit cursors are used for SQL statements that are not named.
2. Developers should use implicit cursors with great care.
3. Implicit cursors are used in cursor for loops to handle data processing.
4. Implicit cursors are no longer a feature in Oracle.
2. Which of the following is not a feature of a cursor FOR loop?
1. Record type declaration.
2. Opening and parsing of SQL statements.
3. Fetches records from cursor.
4. Requires exit condition to be defined.
3. A developer would like to use referential datatype declaration on a variable. The variable name is EMPLOYEE_LASTNAME, and the corresponding table and column is EMPLOYEE, and LNAME, respectively. How would the developer define this variable using referential datatypes?
1. Use employee.lname%type.
2. Use employee.lname%rowtype.
3. Look up datatype for EMPLOYEE column on LASTNAME table and use that.
4. Declare it to be type LONG.
4. Which three of the following are implicit cursor attributes?
1. %found
2. %too_many_rows
3. %notfound
4. %rowcount
5. %rowtype
5. If left out, which of the following would cause an infinite loop to occur in a simple loop?
1. LOOP
2. END LOOP
3. IF-THEN
4. EXIT
6. Which line in the following statement will produce an error?
1. cursor action_cursor is
2. select name, rate, action
3. into action_record
4. from action_table;
5. There are no errors in this statement.
7. The command used to open a CURSOR FOR loop is
1. open
2. fetch
3. parse
4. None, cursor for loops handle cursor opening implicitly.
8. What happens when rows are found using a FETCH statement
1. It causes the cursor to close
2. It causes the cursor to open
3. It loads the current row values into variables
4. It creates the variables to hold the current row values
9. Read the following code:
CREATE OR REPLACE PROCEDURE find_cpt
(v_movie_id {Argument Mode} NUMBER, v_cost_per_ticket {argument mode} NUMBER)
IS
BEGIN
IF v_cost_per_ticket > 8.5 THEN
SELECT cost_per_ticket
INTO v_cost_per_ticket
FROM gross_receipt
WHERE movie_id = v_movie_id;
END IF;
END;
Which mode should be used for V_COST_PER_TICKET?
1. IN
2. OUT
3. RETURN
4. IN OUT
10. Read the following code:
CREATE OR REPLACE TRIGGER update_show_gross
{trigger information}
BEGIN
{additional code}
END;
The trigger code should only execute when the column, COST_PER_TICKET, is greater than $3. Which trigger information will you add?
1. WHEN (new.cost_per_ticket > 3.75)
2. WHEN (:new.cost_per_ticket > 3.75
3. WHERE (new.cost_per_ticket > 3.75)
4. WHERE (:new.cost_per_ticket > 3.75)
11. What is the maximum number of handlers processed before the PL/SQL block is exited when an exception occurs?
1. Only one
2. All that apply
3. All referenced
4. None
12. For which trigger timing can you reference the NEW and OLD qualifiers?
1. Statement and Row
2. Statement only
3. Row only
4. Oracle Forms trigger
13. Read the following code:
CREATE OR REPLACE FUNCTION get_budget(v_studio_id IN NUMBER)
RETURN number IS
v_yearly_budget NUMBER;
BEGIN
SELECT yearly_budget
INTO v_yearly_budget
FROM studio
WHERE id = v_studio_id;
RETURN v_yearly_budget;
END;
Which set of statements will successfully invoke this function within SQL*Plus?
1. VARIABLE g_yearly_budget NUMBER
EXECUTE g_yearly_budget := GET_BUDGET(11);
2. VARIABLE g_yearly_budget NUMBER
EXECUTE :g_yearly_budget := GET_BUDGET(11);
3. VARIABLE :g_yearly_budget NUMBER
EXECUTE :g_yearly_budget := GET_BUDGET(11);
4. VARIABLE g_yearly_budget NUMBER
:g_yearly_budget := GET_BUDGET(11);
14.
CREATE OR REPLACE PROCEDURE update_theater
(v_name IN VARCHAR v_theater_id IN NUMBER) IS
BEGIN
UPDATE theater
SET name = v_name
WHERE id = v_theater_id;
END update_theater;
When invoking this procedure, you encounter the error:
ORA-000: Unique constraint(SCOTT.THEATER_NAME_UK) violated.
How should you modify the function to handle this error?
1. An user defined exception must be declared and associated with the error code and handled in the EXCEPTION section.
2. Handle the error in EXCEPTION section by referencing the error code directly.
3. Handle the error in the EXCEPTION section by referencing the UNIQUE_ERROR predefined exception.
4. Check for success by checking the value of SQL%FOUND immediately after the UPDATE statement.
15. Read the following code:
CREATE OR REPLACE PROCEDURE calculate_budget IS
v_budget studio.yearly_budget%TYPE;
BEGIN
v_budget := get_budget(11);
IF v_budget < 30000
THEN
set_budget(11,30000000);
END IF;
END;
You are about to add an argument to CALCULATE_BUDGET. What effect will this have?
1. The GET_BUDGET function will be marked invalid and must be recompiled before the next execution.
2. The SET_BUDGET function will be marked invalid and must be recompiled before the next execution.
3. Only the CALCULATE_BUDGET procedure needs to be recompiled.
4. All three procedures are marked invalid and must be recompiled.
16. Which procedure can be used to create a customized error message?
1. RAISE_ERROR
2. SQLERRM
3. RAISE_APPLICATION_ERROR
4. RAISE_SERVER_ERROR
17. The CHECK_THEATER trigger of the THEATER table has been disabled. Which command can you issue to enable this trigger?
1. ALTER TRIGGER check_theater ENABLE;
2. ENABLE TRIGGER check_theater;
3. ALTER TABLE check_theater ENABLE check_theater;
4. ENABLE check_theater;
18. Examine this database trigger
CREATE OR REPLACE TRIGGER prevent_gross_modification
{additional trigger information}
BEGIN
IF TO_CHAR(sysdate, DY) = MON
THEN
RAISE_APPLICATION_ERROR(-20000,Gross receipts cannot be deleted on Monday);
END IF;
END;
This trigger must fire before each DELETE of the GROSS_RECEIPT table. It should fire only once for the entire DELETE statement. What additional information must you add?
1. BEFORE DELETE ON gross_receipt
2. AFTER DELETE ON gross_receipt
3. BEFORE (gross_receipt DELETE)
4. FOR EACH ROW DELETED FROM gross_receipt
19. Examine this function:
CREATE OR REPLACE FUNCTION set_budget
(v_studio_id IN NUMBER, v_new_budget IN NUMBER) IS
BEGIN
UPDATE studio
SET yearly_budget = v_new_budget
WHERE id = v_studio_id;
IF SQL%FOUND THEN
RETURN TRUEl;
ELSE
RETURN FALSE;
END IF;
COMMIT;
END;
Which code must be added to successfully compile this function?
1. Add RETURN right before the IS keyword.
2. Add RETURN number right before the IS keyword.
3. Add RETURN boolean right after the IS keyword.
4. Add RETURN boolean right before the IS keyword.
20. Under which circumstance must you recompile the package body after recompiling the package specification?
1. Altering the argument list of one of the package constructs
2. Any change made to one of the package constructs
3. Any SQL statement change made to one of the package constructs
4. Removing a local variable from the DECLARE section of one of the package constructs
21. Procedure and Functions are explicitly executed. This is different from a database trigger. When is a database trigger executed?
1. When the transaction is committed
2. During the data manipulation statement
3. When an Oracle supplied package references the trigger
4. During a data manipulation statement and when the transaction is committed
22. Which Oracle supplied package can you use to output values and messages from database triggers, stored procedures and functions within SQL*Plus?
1. DBMS_DISPLAY
2. DBMS_OUTPUT
3. DBMS_LIST
4. DBMS_DESCRIBE
23. What occurs if a procedure or function terminates with failure without being handled?
1. Any DML statements issued by the construct are still pending and can be committed or rolled back.
2. Any DML statements issued by the construct are committed
3. Unless a GOTO statement is used to continue processing within the BEGIN section, the construct terminates.
4. The construct rolls back any DML statements issued and returns the unhandled exception to the calling environment.
24. Examine this code
BEGIN
theater_pck.v_total_seats_sold_overall := theater_pck.get_total_for_year;
END;
For this code to be successful, what must be true?
1. Both the V_TOTAL_SEATS_SOLD_OVERALL variable and the GET_TOTAL_FOR_YEAR function must exist only in the body of the THEATER_PCK package.
2. Only the GET_TOTAL_FOR_YEAR variable must exist in the specification of the THEATER_PCK package.
3. Only the V_TOTAL_SEATS_SOLD_OVERALL variable must exist in the specification of the THEATER_PCK package.
4. Both the V_TOTAL_SEATS_SOLD_OVERALL variable and the GET_TOTAL_FOR_YEAR function must exist in the specification of the THEATER_PCK package.
25. A stored function must return a value based on conditions that are determined at runtime. Therefore, the SELECT statement cannot be hard-coded and must be created dynamically when the function is executed. Which Oracle supplied package will enable this feature?
1. DBMS_DDL
2. DBMS_DML
3. DBMS_SYN
4. DBMS_SQL
Ans:- 1.1
2.2
3.1
4.(1,3,4)
5.2
6.3
7.4
8.2
9.2
10.(3,4)
11.1
12.4
13.1
14.1
15.3
16.3
17.1
18.(1,4)
19.4
20.3
21.4
22.2
23.4
24.3
25.4...................
1.What is the SQL?
SQL stands for Structure Query Language. SQL is an English like language consisting of commands to store, retrieve, maintain & regulate access to your database.
2.What is SQL*Plus?
SQL*Plus is an application that recognizes & executes SQL commands & specialized SQL*Plus commands that can customize reports, provide help & edit facility & maintain system variables.
3.What is NVL?
NVL : Null value function converts a null value to a non-null value for the purpose of evaluating an expression. Numeric Functions accept numeric I/P & return numeric values. They are MOD, SQRT, ROUND, TRUNC & POWER.
4. What is Date Functions?
Date Functions are ADD_MONTHS, LAST_DAY, NEXT_DAY, MONTHS_BETWEEN & SYSDATE.
5.What is Character Functions?
Character Functions are INITCAP, UPPER, LOWER, SUBSTR & LENGTH. Additional functions are GREATEST & LEAST. Group Functions returns results based upon groups of rows rather than one result per row, use group functions. They are AVG, COUNT, MAX, MIN & SUM.
6. What is TTITLE and BTITLE?
TTITLE & BTITLE are commands to control report headings & footers.
7. What is COLUMN?
COLUMN command define column headings & format data values.
8.What is BREAK?
BREAK command clarify reports by suppressing repeated values, skipping lines & allowing for controlled break points.
9. What is COMPUTE?
command control computations on subsets created by the BREAK command.
10. What is SET?
SET command changes the system variables affecting the report environment.
11. What is SPOOL?
SPOOL command creates a print file of the report.
12.What is a JOIN?
JOIN is the form of SELECT command that combines info from two or more tables.
Types of Joins are Simple (Equijoin & Non-Equijoin), Outer & Self join.
Equijoin returns rows from two or more tables joined together based upon a equality condition in the WHERE clause.
Non-Equijoin returns rows from two or more tables based upon a relationship other than the equality condition in the WHERE clause.
Outer Join combines two or more tables returning those rows from one table that have no direct match in the other table.
Self Join joins a table to itself as though it were two separate tables.
13. What is Union?
Union is the product of two or more tables.
14. What is Intersect?
Intersect is the product of two tables listing only the matching rows.
15. What is Minus?
Minus is the product of two tables listing only the non-matching rows.
16.What is Correlated Subquery?
Correlated Subquery is a subquery that is evaluated once for each row processed by the parent statement. Parent statement can be Select, Update or Delete. Use CRSQ to answer multipart questions whose answer depends on the value in each row processed by parent statement.
17. What is Multiple columns?
Multiple columns can be returned from a Nested Subquery.
18.What is Sequences?
Sequences are used for generating sequence numbers without any overhead of locking. Drawback is that after generating a sequence number if the transaction is rolled back, then that sequence number is lost.
19.What is Synonyms?
Synonyms is the alias name for table, views, sequences & procedures and are created for reasons of Security and Convenience.
Two levels are Public - created by DBA & accessible to all the users. Private - Accessible to creator only. Advantages are referencing without specifying the owner and Flexibility to customize a more meaningful naming convention.
20.What is Indexes?
Indexes are optional structures associated with tables used to speed query execution and/or guarantee uniqueness. Create an index if there are frequent retrieval of fewer than 10-15% of the rows in a large table and columns are referenced frequently in the WHERE clause. Implied tradeoff is query speed vs. update speed. Oracle automatically update indexes. Concatenated index max. is 16 columns.
21.What is Data types?
Max. columns in a table is 255. Max. Char size is 255, Long is 64K & Number is 38 digits.
Cannot Query on a long column.
Char, Varchar2 Max. size is 2000 & default is 1 byte.
Number(p,s) p is precision range 1 to 38, s is scale -84 to 127.
Long Character data of variable length upto 2GB.
Date Range from Jan 4712 BC to Dec 4712 AD.
Raw Stores Binary data (Graphics Image & Digitized Sound). Max. is 255 bytes.
Mslabel Binary format of an OS label. Used primarily with Trusted Oracle.
22. Order of SQL statement execution?
Where clause, Group By clause, Having clause, Order By clause & Select.
23.What is Transaction?
Transaction is defined as all changes made to the database between successive commits.
24.What is Commit?
Commit is an event that attempts to make data in the database identical to the data in the form. It involves writing or posting data to the database and committing data to the database. Forms check the validity of the data in fields and records during a commit. Validity check are uniqueness, consistency and db restrictions.
25.What is Posting?
Posting is an event that writes Inserts, Updates & Deletes in the forms to the database but not committing these transactions to the database.
26.What is Rollback?
Rollback causes work in the current transaction to be undone.
27.What is Savepoint?
Savepoint is a point within a particular transaction to which you may rollback without rolling back the entire transaction.
28. What is Set Transaction?
Set Transaction is to establish properties for the current transaction.
29.What is Locking?
Locking are mechanisms intended to prevent destructive interaction between users accessing data. Locks are used to achieve.
30. What is Consistency?
Consistency : Assures users that the data they are changing or viewing is not changed until the are thro' with it.
31.What is SQL Integrity?
Assures database data and structures reflects all changes made to them in the correct sequence. Locks ensure data integrity and maximum concurrent access to data. Commit statement releases all locks. Types of locks are given below.
Data Locks protects data i.e. Table or Row lock.
Dictionary Locks protects the structure of database object i.e. ensures table's structure does not change for the duration of the transaction.
Internal Locks & Latches protects the internal database structures. They are automatic.
Exclusive Lock allows queries on locked table but no other activity is allowed.
Share Lock allows concurrent queries but prohibits updates to the locked tables.
Row Share allows concurrent access to the locked table but prohibits for a exclusive table lock.
Row Exclusive same as Row Share but prohibits locking in shared mode.
Shared Row Exclusive locks the whole table and allows users to look at rows in the table but prohibit others from locking the table in share or updating them.
Share Update are synonymous with Row Share.
32.What is SQL Deadlock?
Deadlock is a unique situation in a multi user system that causes two or more users to wait indefinitely for a locked resource. First user needs a resource locked by the second user and the second user needs a resource locked by the first user. To avoid dead locks, avoid using exclusive table lock and if using, use it in the same sequence and use Commit frequently to release locks.
33. What is Mutating SQL Table?
Mutating Table is a table that is currently being modified by an Insert, Update or Delete statement. Constraining Table is a table that a triggering statement might need to read either directly for a SQL statement or indirectly for a declarative Referential Integrity constraints. Pseudo Columns behaves like a column in a table but are not actually stored in the table. E.g. Currval, Nextval, Rowid, Rownum, Level etc.
34.What is SQL*Loader?
SQL*Loader is a product for moving data in external files into tables in an Oracle database. To load data from external files into an Oracle database, two types of input must be provided to SQL*Loader : the data itself and the control file. The control file describes the data to be loaded. It describes the Names and format of the data files, Specifications for loading data and the Data to be loaded (optional). Invoking the loader sqlload username/password controlfilename <options>.
35.The most important DDL statements in SQL are?
CREATE TABLE - creates a new database table
ALTER TABLE - alters (changes) a database table
DROP TABLE - deletes a database table
CREATE INDEX - creates an index (search key)
DROP INDEX - deletes an index
36. Operators used in SELECT statements are?
= Equal
<> or != Not equal
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
BETWEEN Between an inclusive range
LIKE Search for a pattern
37.SELECT statements in SQL?
SELECT column_name(s) FROM table_name
SELECT DISTINCT column_name(s) FROM table_name
SELECT column FROM table WHERE column operator value
SELECT column FROM table WHERE column LIKE pattern
SELECT column,SUM(column) FROM table GROUP BY column
SELECT column,SUM(column) FROM table GROUP BY column HAVING SUM(column) condition value
Note that single quotes around text values and numeric values should not be enclosed in quotes. Double quotes may be acceptable in some databases.
38.The SELECT INTO Statement is most often used to create backup copies of tables or for archiving records?
SELECT column_name(s) INTO newtable [IN externaldatabase] FROM source
SELECT column_name(s) INTO newtable [IN externaldatabase] FROM source WHERE column_name operator value
39.The INSERT INTO Statements in SQL?
INSERT INTO table_name VALUES (value1, value2,....)
INSERT INTO table_name (column1, column2,...) VALUES (value1, value2,....)
40. The Update Statement in SQL.?
UPDATE table_name SET column_name = new_value WHERE column_name = some_value
41. The Delete Statements in SQL.?
DELETE FROM table_name WHERE column_name = some_value
Delete All Rows:
DELETE FROM table_name or DELETE * FROM table_name
41. Sort the Rows in SQL.?
Sort the Rows:
SELECT column1, column2, ... FROM table_name ORDER BY columnX, columnY, ..
SELECT column1, column2, ... FROM table_name ORDER BY columnX DESC
SELECT column1, column2, ... FROM table_name ORDER BY columnX DESC, columnY ASC
42.The IN operator may be used if you know the exact value you want to return for at least one of the columns.?
SELECT column_name FROM table_name WHERE column_name IN (value1,value2,..)
43. BETWEEN ... AND operators in SQL.?
SELECT column_name FROM table_name WHERE column_name BETWEEN value1 AND value2 The values can be numbers, text, or dates.
44.What is the use of CASCADE CONSTRAINTS?
When this clause is used with the DROP command, a parent table can be dropped even when a child table exists.
Oracle SQL & PL/SQL
45.What Is SQL?
SQL (pronounced as the letters S-Q-L or as sequel) is an abbreviation for Structured Query Language. SQL is a language designed specifically for communicating with databases. SQL is designed to do one thing and do it well—provide you with a simple and efficient way to read and write data from a database.
46.Which command displays the SQL command in the SQL buffer, and then executes it?
RUN
47.What is the difference between Truncate & Drop?
48.Explain SQL Having?
49.Difference between SQL Having & Where?
50.Difference between SQL IN/SQL Exists?
51.Difference between SQL NOT IN/SQL NOT Exists?
52.Difference between SQL UNION/SQL UNION ALL?
53.Explain SQL TOP.
54.How to delete duplicate records in a table?
55.How to find duplicate records with the number they are duplicated?
SELECT Id, count (*) as num_records
from table
group by id
having count (*) > 1
56.What is a PRIMARY KEY?
The PRIMARY KEY is the column(s) used to uniquely identify each row of a table.
57.What is a FOREIGN KEY?
A FOREIGN KEY is one or more columns whose values are based on the PRIMARY or CANDIDATE KEY values from the database.
58.What is a UNIQUE KEY?
A UNIQUE KEY is one or more columns that must be unique for each row of the table.
59.What is the difference between UNIQUE and PRIMARY KEY?
The UNIQUE KEY column restricts entry of duplicate values but entry of NULL value is allowed. In case of PRIMARY KEY columns entry of duplicate as well as <null> value is also restricted.
60.Difference between Unique Key and Primary Key.?
61.Difference between Cast & Convert.?
62.Explain SQL Group by and give examples.?
63.How can you call a PL/SQL procedure from SQL?
By use of the EXECUTE (short form EXEC) command.
64.Which is the subset of SQL commands used to manipulate Oracle Database structures?
Data Definition Language (DDL)
65.Write a query to select the Nth highest salary from a table.?
66.Write a query to select the 2nd highest salary from a table.?
67.Write a query to select the second highest salary from a table.?
SELECT max(salary) AS salary_2
FROM emp
WHERE salary < (SELECT max(salary) AS salary_1
FROM emp)
68.Write a query to select the 5th highest salary from a table.?
SELECT min(salary) AS high5
FROM employee
WHERE salary IN(SELECT DISTINCT TOP 5 salary
FROM employee
ORDER BY salary DESC)
69.What command is used to get back the privileges offered by the GRANT command?
Revoke
70.How do you execute a host operating system command from within SQL?
By use of the exclamation point “!” (in UNIX and some other OS) or the HOST (HO) command.
71.What command is used to create a table by copying the structure of another table?
CREATE TABLE .. AS SELECT command
72.Give examples of Create Table?
73.What is the difference between Delete and Truncate command in SQL?
74.What is the difference between Delete and Truncate command in SQL?
Delete command and truncate command both will delete the data, however the truncate command can not be rolled back as delete can be. TRUNCATE is a DDL command whereas DELETE is a DML command. The delete command can be used for selected records using the where clause but with the truncate command we have to loose data. DELETE statement is a logged operation and hence takes more time then truncate.
75.How can variables be passed to a SQL routine?
By use of the & symbol. For passing in variables the numbers 1-8 can be used (&1, &2,...,&8) to pass the values after the command into the SQLPLUS session. To be prompted for a specific variable, place the ampersanded variable in the code itself: “select * from dba_tables where owner=&owner_name;” . Use of double ampersands tells SQLPLUS to resubstitute the value for each subsequent use of the variable, a single ampersand will cause a reprompt for the value unless an ACCEPT statement is used to get the value from the user.
76.What SQLPlus command is used to format output from a select?
This is best done with the COLUMN command.
77.Can Primary key is a Foreign Key on the same table?
Yes
78.You want to determine the location of identical rows in a table before attempting to place a unique index on the table, how can this be done?
Oracle tables always have one guaranteed unique column, the rowid column. If you use a min/max function against your rowid and then select against the proposed primary key you can squeeze out the rowids of the duplicate rows pretty quick. For example:
select rowid from emp e
where e.rowid > (select min(x.rowid)
from emp x
where x.emp_no = e.emp_no);
79.What is the use of the DROP option in the ALTER TABLE command?
It is used to drop constraints specified on the table.
80.What is a Cartesian product?
A Cartesian product is the result of an unrestricted join of two or more tables. The result set of a three table Cartesian product will have x * y * z number of rows where x, y, z correspond to the number of rows in each table involved in the join.
81.How do you prevent output from coming to the screen?
The SET option TERMOUT controls output to the screen. Setting TERMOUT OFF turns off screen output. This option can be shortened to TERM.
82.What is the use of CASCADE CONSTRAINTS?
When this clause is used with the DROP command, a parent table can be dropped even when a child table exists.
83.Which function is used to find the largest integer less than or equal to a specific value?
FLOOR
Consider the below DEPT and EMPLOYEE table and answer the below queries.
DEPT
DEPTNO (NOT NULL , NUMBER(2)),
DNAME (VARCHAR2(14)),
LOC (VARCHAR2(13)
EMPLOYEE
EMPNO (NOT NULL , NUMBER(4)),
ENAME (VARCHAR2(10)),
JOB (VARCHAR2(9)),
MGR (NUMBER(4)),
HIREDATE (DATE),
SAL (NUMBER(7,2)),
COMM (NUMBER(7,2)),
DEPTNO (NUMBER(2))
MGR is the EMPno of the Employee whom the Employee reports to.
DEPTNO is a foreign key.
1. List all the Employees who have at least one person reporting to them.
SELECT ENAME FROM EMPLOYEE WHERE EMPNO IN (SELECT MGR FROM EMPLOYEE);
2. List the highest salary paid for each job.
SELECT JOB, MAX(SAL) FROM EMPLOYEE GROUP BY JOB
3. In which year did most people join the company? Display the year and the number of Employees.
SELECT TO_CHAR(HIREDATE,'YYYY') "YEAR", COUNT(EMPNO) "NO. OF EMPLOYEES"
FROM EMPLOYEE
GROUP BY TO_CHAR(HIREDATE,'YYYY')
HAVING COUNT(EMPNO) = (SELECT MAX(COUNT(EMPNO))
FROM EMPLOYEE
GROUP BY TO_CHAR(HIREDATE,'YYYY'));
4. Write a correlated sub-query to list out the Employees who earn more than the average salary of their department.
SELECT ENAME,SAL
FROM EMPLOYEE E
WHERE SAL > (SELECT AVG(SAL)
FROM EMPLOYEE F
WHERE E.DEPTNO = F.DEPTNO);
5. Find the nth maximum salary.
SELECT ENAME, SAL
FROM EMPLOYEE A
WHERE &N = (SELECT COUNT (DISTINCT(SAL))
FROM EMPLOYEE B
WHERE A.SAL<=B.SAL);
6. Select the duplicate records (Records, which are inserted, that already exist) in the EMPLOYEE table.
SELECT * FROM EMPLOYEE A
WHERE A.EMPNO IN (SELECT EMPNO
FROM EMPLOYEE
GROUP BY EMPNO
HAVING COUNT(EMPNO)>1)
AND A.ROWID!=MIN (ROWID));
7. Write a query to list the length of service of the Employees (of the form n years and m months).
SELECT ENAME "EMPLOYEE",TO_CHAR(TRUNC(MONTHS_BETWEEN(SYSDATE,HIREDATE)/12))
||' YEARS '|| TO_CHAR(TRUNC(MOD(MONTHS_BETWEEN
(SYSDATE, HIREDATE),12)))||' MONTHS ' "LENGTH OF SERVICE"
FROM EMPLOYEE;
Ans. PL/SQL is a procedural language that has both interactive SQL and procedural programming language constructs such as iteration, conditional branching.
2. What is the basic structure of PL/SQL ?
Ans. PL/SQL uses block structure as its basic structure. Anonymous blocks or
nested blocks can be used in PL/SQL.3. What are the components of a PL/SQL block ?
Ans. A set of related declarations and procedural statements is called block.
4. What are the components of a PL/SQL Block ?
Ans. Declarative part, Executable part and Exception part.
Datatypes PL/SQL
5. What are the datatypes a available in PL/SQL ?
Ans. Some scalar data types such as NUMBER, VARCHAR2, DATE, CHAR, LONG, BOOLEAN.
Some composite data types such as RECORD & TABLE.
6. What are % TYPE and % ROWTYPE ? What are the advantages of using these over datatypes?
Ans. % TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are : I. Need not know about variable’s data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.
7. What is difference between % ROWTYPE and TYPE RECORD ?
Ans. % ROWTYPE is to be used whenever query returns a entire row of a table or view.
TYPE rec RECORD is to be used whenever query returns columns of different
table or views and variables.
E.g. TYPE r_emp is RECORD (eno emp.empno% type,ename emp ename %type
);
e_rec emp% ROWTYPE
cursor c1 is select empno,deptno from emp;
e_rec c1 %ROWTYPE.
8. What is PL/SQL table ?
Ans. Objects of type TABLE are called “PL/SQL tables”, which are modeled as (but not the same as) database tables, PL/SQL tables use a primary PL/SQL tables can have one column and a primary key.
9. What is a cursor ? Why Cursor is required ?
Ans. Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.
10. Explain the two type of Cursors ?
There are two types of cursors, Implicit Cursor and Explicit Cursor.
PL/SQL uses Implicit Cursors for queries.
User defined cursors are called Explicit Cursors. They can be declared and used.
11. What are the PL/SQL Statements used in cursor processing ?
Ans. DECLARE CURSOR cursor name, OPEN cursor name, FETCH cursor name INTO or Record types, CLOSE cursor name.
12. What are the cursor attributes used in PL/SQL ?
Ans. %ISOPEN – to check whether cursor is open or not
% ROWCOUNT – number of rows fetched/updated/deleted.
% FOUND – to check whether cursor has fetched any row. True if rows are fetched.
% NOT FOUND – to check whether cursor has fetched any row. True if no rows are fetched.
These attributes are proceeded with SQL for Implicit Cursors and with Cursor name for Explicit Cursors.
13. What is a cursor for loop ?
Ans. Cursor for loop implicitly declares %ROWTYPE as loop index, opens a cursor, fetches rows of values from active set into fields in the record and closes
when all the records have been processed.
eg. FOR emp_rec IN C1 LOOP
salary_total := salary_total +emp_rec sal;
END LOOP;
14. What will happen after commit statement ?
Ans. Cursor C1 is
Select empno,
ename from emp;
Begin
open C1; loop
Fetch C1 into
eno.ename;
Exit When
C1 %notfound;—–
commit;
end loop;
end; The cursor having query as SELECT …. FOR UPDATE gets closed after COMMIT/ROLLBACK.
The cursor having query as SELECT…. does not get closed even after COMMIT/ROLLBACK.
15. Explain the usage of WHERE CURRENT OF clause in cursors ?
Ans. WHERE CURRENT OF clause in an UPDATE, DELETE statement refers to the latest row fetched from a cursor.
16. What is a database trigger ? Name some usages of database trigger ?
Ans. Database trigger is stored PL/SQL program unit associated with a specific database table. Usages are Audit data modifications, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.
17. How many types of database triggers can be specified on a table ? What are they ?
Ans. Insert Update Delete
Before Row o.k. o.k. o.k.
After Row o.k. o.k. o.k.
Before Statement o.k. o.k. o.k.
After Statement o.k. o.k. o.k.
If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.
If WHEN clause is specified, the trigger fires according to the returned boolean value.
18. Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger ? Why ?
Ans.It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing.
19. What are two virtual tables available during database trigger execution ?
Ans. The table columns are referred as OLD.column_name and NEW.column_name.
For triggers related to INSERT only NEW.column_name values only available.
For triggers related to UPDATE only OLD.column_name NEW.column_name values only available.
For triggers related to DELETE only OLD.column_name values only available.
20. What happens if a procedure that updates a column of table X is called in a database trigger of the same table ?
Ans. Mutation of table occurs.
21. What is an Exception ? What are types of Exception ?
Ans. Exception is the error handling part of PL/SQL block. The types are Predefined and user_defined. Some of Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
22. What is Pragma EXECPTION_INIT ? Explain the usage ?
Ans. The PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. To get an error message of a specific oracle error.
e.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number)
23. What is Raise_application_error ?
Ans. Raise_application_error is a procedure of package DBMS_STANDARD which allows to issue an user_defined error messages from stored sub-program or database trigger.
24. What are the return values of functions SQLCODE and SQLERRM ?
Ans. SQLCODE returns the latest code of the error that has occurred.
SQLERRM returns the relevant error message of the SQLCODE.
25. Where the Pre_defined_exceptions are stored ?
Ans. In the standard package.
26. What is a stored procedure ?
Ans. A stored procedure is a sequence of statements that perform specific function.
27. What is difference between a PROCEDURE & FUNCTION ?
Ans. A FUNCTION always returns a value using the return statement.
A PROCEDURE may return one or more values through parameters or may not return at all.
28. What are advantages fo Stored Procedures ?
Ans. Extensibility, Modularity, Reusability, Maintainability and one time compilation.
29. What are the modes of parameters that can be passed to a procedure ?
Ans. IN, OUT, IN-OUT parameters.
30. What are the two parts of a procedure ?
Ans. Procedure Specification and Procedure Body.
31. Give the structure of the procedure ?
Ans. PROCEDURE name (parameter list…..)
is
local variable declarations
BEGIN
Executable statements.
Exception.
exception handlers
end;
32. Give the structure of the function ?
Ans. FUNCTION name (argument list …..) Return datatype is
local variable declarations
Begin
executable statements
Exception
execution handlers
End;
33. Explain how procedures and functions are called in a PL/SQL block ?
Ans. Function is called as part of an expression.
sal := calculate_sal (‘a822′);
procedure is called as a PL/SQL statement
calculate_bonus (‘A822′);
34. What is Overloading of procedures ?
Ans. The Same procedure name is repeated with parameters of different datatypes and parameters in different positions, varying number of parameters is called overloading of procedures.
e.g. DBMS_OUTPUT put_line
35. What is a package ? What are the advantages of packages ?
Ans. Package is a database object that groups logically related procedures.
The advantages of packages are Modularity, Easier Application Design, Information. Hiding,. reusability and Better Performance.
36.What are two parts of package ?
Ans. The two parts of package are PACKAGE SPECIFICATION & PACKAGE BODY.
Package Specification contains declarations that are global to the packages and local to the schema.
Package Body contains actual procedures and local declaration of the procedures and cursor declarations.
37. What is difference between a Cursor declared in a procedure and Cursor declared in a package specification ?
Ans. A cursor declared in a package specification is global and can be accessed by other procedures or procedures in a package.
A cursor declared in a procedure is local to the procedure that can not be accessed by other procedures.
38. Name the tables where characteristics of Package, procedure and functions are stored ?
Ans. User_objects, User_Source and User_error .....
PL/SQL interview qiuestions:-
1. Which of the following statements is true about implicit cursors?
1. Implicit cursors are used for SQL statements that are not named.
2. Developers should use implicit cursors with great care.
3. Implicit cursors are used in cursor for loops to handle data processing.
4. Implicit cursors are no longer a feature in Oracle.
2. Which of the following is not a feature of a cursor FOR loop?
1. Record type declaration.
2. Opening and parsing of SQL statements.
3. Fetches records from cursor.
4. Requires exit condition to be defined.
3. A developer would like to use referential datatype declaration on a variable. The variable name is EMPLOYEE_LASTNAME, and the corresponding table and column is EMPLOYEE, and LNAME, respectively. How would the developer define this variable using referential datatypes?
1. Use employee.lname%type.
2. Use employee.lname%rowtype.
3. Look up datatype for EMPLOYEE column on LASTNAME table and use that.
4. Declare it to be type LONG.
4. Which three of the following are implicit cursor attributes?
1. %found
2. %too_many_rows
3. %notfound
4. %rowcount
5. %rowtype
5. If left out, which of the following would cause an infinite loop to occur in a simple loop?
1. LOOP
2. END LOOP
3. IF-THEN
4. EXIT
6. Which line in the following statement will produce an error?
1. cursor action_cursor is
2. select name, rate, action
3. into action_record
4. from action_table;
5. There are no errors in this statement.
7. The command used to open a CURSOR FOR loop is
1. open
2. fetch
3. parse
4. None, cursor for loops handle cursor opening implicitly.
8. What happens when rows are found using a FETCH statement
1. It causes the cursor to close
2. It causes the cursor to open
3. It loads the current row values into variables
4. It creates the variables to hold the current row values
9. Read the following code:
CREATE OR REPLACE PROCEDURE find_cpt
(v_movie_id {Argument Mode} NUMBER, v_cost_per_ticket {argument mode} NUMBER)
IS
BEGIN
IF v_cost_per_ticket > 8.5 THEN
SELECT cost_per_ticket
INTO v_cost_per_ticket
FROM gross_receipt
WHERE movie_id = v_movie_id;
END IF;
END;
Which mode should be used for V_COST_PER_TICKET?
1. IN
2. OUT
3. RETURN
4. IN OUT
10. Read the following code:
CREATE OR REPLACE TRIGGER update_show_gross
{trigger information}
BEGIN
{additional code}
END;
The trigger code should only execute when the column, COST_PER_TICKET, is greater than $3. Which trigger information will you add?
1. WHEN (new.cost_per_ticket > 3.75)
2. WHEN (:new.cost_per_ticket > 3.75
3. WHERE (new.cost_per_ticket > 3.75)
4. WHERE (:new.cost_per_ticket > 3.75)
11. What is the maximum number of handlers processed before the PL/SQL block is exited when an exception occurs?
1. Only one
2. All that apply
3. All referenced
4. None
12. For which trigger timing can you reference the NEW and OLD qualifiers?
1. Statement and Row
2. Statement only
3. Row only
4. Oracle Forms trigger
13. Read the following code:
CREATE OR REPLACE FUNCTION get_budget(v_studio_id IN NUMBER)
RETURN number IS
v_yearly_budget NUMBER;
BEGIN
SELECT yearly_budget
INTO v_yearly_budget
FROM studio
WHERE id = v_studio_id;
RETURN v_yearly_budget;
END;
Which set of statements will successfully invoke this function within SQL*Plus?
1. VARIABLE g_yearly_budget NUMBER
EXECUTE g_yearly_budget := GET_BUDGET(11);
2. VARIABLE g_yearly_budget NUMBER
EXECUTE :g_yearly_budget := GET_BUDGET(11);
3. VARIABLE :g_yearly_budget NUMBER
EXECUTE :g_yearly_budget := GET_BUDGET(11);
4. VARIABLE g_yearly_budget NUMBER
:g_yearly_budget := GET_BUDGET(11);
14.
CREATE OR REPLACE PROCEDURE update_theater
(v_name IN VARCHAR v_theater_id IN NUMBER) IS
BEGIN
UPDATE theater
SET name = v_name
WHERE id = v_theater_id;
END update_theater;
When invoking this procedure, you encounter the error:
ORA-000: Unique constraint(SCOTT.THEATER_NAME_UK) violated.
How should you modify the function to handle this error?
1. An user defined exception must be declared and associated with the error code and handled in the EXCEPTION section.
2. Handle the error in EXCEPTION section by referencing the error code directly.
3. Handle the error in the EXCEPTION section by referencing the UNIQUE_ERROR predefined exception.
4. Check for success by checking the value of SQL%FOUND immediately after the UPDATE statement.
15. Read the following code:
CREATE OR REPLACE PROCEDURE calculate_budget IS
v_budget studio.yearly_budget%TYPE;
BEGIN
v_budget := get_budget(11);
IF v_budget < 30000
THEN
set_budget(11,30000000);
END IF;
END;
You are about to add an argument to CALCULATE_BUDGET. What effect will this have?
1. The GET_BUDGET function will be marked invalid and must be recompiled before the next execution.
2. The SET_BUDGET function will be marked invalid and must be recompiled before the next execution.
3. Only the CALCULATE_BUDGET procedure needs to be recompiled.
4. All three procedures are marked invalid and must be recompiled.
16. Which procedure can be used to create a customized error message?
1. RAISE_ERROR
2. SQLERRM
3. RAISE_APPLICATION_ERROR
4. RAISE_SERVER_ERROR
17. The CHECK_THEATER trigger of the THEATER table has been disabled. Which command can you issue to enable this trigger?
1. ALTER TRIGGER check_theater ENABLE;
2. ENABLE TRIGGER check_theater;
3. ALTER TABLE check_theater ENABLE check_theater;
4. ENABLE check_theater;
18. Examine this database trigger
CREATE OR REPLACE TRIGGER prevent_gross_modification
{additional trigger information}
BEGIN
IF TO_CHAR(sysdate, DY) = MON
THEN
RAISE_APPLICATION_ERROR(-20000,Gross receipts cannot be deleted on Monday);
END IF;
END;
This trigger must fire before each DELETE of the GROSS_RECEIPT table. It should fire only once for the entire DELETE statement. What additional information must you add?
1. BEFORE DELETE ON gross_receipt
2. AFTER DELETE ON gross_receipt
3. BEFORE (gross_receipt DELETE)
4. FOR EACH ROW DELETED FROM gross_receipt
19. Examine this function:
CREATE OR REPLACE FUNCTION set_budget
(v_studio_id IN NUMBER, v_new_budget IN NUMBER) IS
BEGIN
UPDATE studio
SET yearly_budget = v_new_budget
WHERE id = v_studio_id;
IF SQL%FOUND THEN
RETURN TRUEl;
ELSE
RETURN FALSE;
END IF;
COMMIT;
END;
Which code must be added to successfully compile this function?
1. Add RETURN right before the IS keyword.
2. Add RETURN number right before the IS keyword.
3. Add RETURN boolean right after the IS keyword.
4. Add RETURN boolean right before the IS keyword.
20. Under which circumstance must you recompile the package body after recompiling the package specification?
1. Altering the argument list of one of the package constructs
2. Any change made to one of the package constructs
3. Any SQL statement change made to one of the package constructs
4. Removing a local variable from the DECLARE section of one of the package constructs
21. Procedure and Functions are explicitly executed. This is different from a database trigger. When is a database trigger executed?
1. When the transaction is committed
2. During the data manipulation statement
3. When an Oracle supplied package references the trigger
4. During a data manipulation statement and when the transaction is committed
22. Which Oracle supplied package can you use to output values and messages from database triggers, stored procedures and functions within SQL*Plus?
1. DBMS_DISPLAY
2. DBMS_OUTPUT
3. DBMS_LIST
4. DBMS_DESCRIBE
23. What occurs if a procedure or function terminates with failure without being handled?
1. Any DML statements issued by the construct are still pending and can be committed or rolled back.
2. Any DML statements issued by the construct are committed
3. Unless a GOTO statement is used to continue processing within the BEGIN section, the construct terminates.
4. The construct rolls back any DML statements issued and returns the unhandled exception to the calling environment.
24. Examine this code
BEGIN
theater_pck.v_total_seats_sold_overall := theater_pck.get_total_for_year;
END;
For this code to be successful, what must be true?
1. Both the V_TOTAL_SEATS_SOLD_OVERALL variable and the GET_TOTAL_FOR_YEAR function must exist only in the body of the THEATER_PCK package.
2. Only the GET_TOTAL_FOR_YEAR variable must exist in the specification of the THEATER_PCK package.
3. Only the V_TOTAL_SEATS_SOLD_OVERALL variable must exist in the specification of the THEATER_PCK package.
4. Both the V_TOTAL_SEATS_SOLD_OVERALL variable and the GET_TOTAL_FOR_YEAR function must exist in the specification of the THEATER_PCK package.
25. A stored function must return a value based on conditions that are determined at runtime. Therefore, the SELECT statement cannot be hard-coded and must be created dynamically when the function is executed. Which Oracle supplied package will enable this feature?
1. DBMS_DDL
2. DBMS_DML
3. DBMS_SYN
4. DBMS_SQL
Ans:- 1.1
2.2
3.1
4.(1,3,4)
5.2
6.3
7.4
8.2
9.2
10.(3,4)
11.1
12.4
13.1
14.1
15.3
16.3
17.1
18.(1,4)
19.4
20.3
21.4
22.2
23.4
24.3
25.4...................
1.What is the SQL?
SQL stands for Structure Query Language. SQL is an English like language consisting of commands to store, retrieve, maintain & regulate access to your database.
2.What is SQL*Plus?
SQL*Plus is an application that recognizes & executes SQL commands & specialized SQL*Plus commands that can customize reports, provide help & edit facility & maintain system variables.
3.What is NVL?
NVL : Null value function converts a null value to a non-null value for the purpose of evaluating an expression. Numeric Functions accept numeric I/P & return numeric values. They are MOD, SQRT, ROUND, TRUNC & POWER.
4. What is Date Functions?
Date Functions are ADD_MONTHS, LAST_DAY, NEXT_DAY, MONTHS_BETWEEN & SYSDATE.
5.What is Character Functions?
Character Functions are INITCAP, UPPER, LOWER, SUBSTR & LENGTH. Additional functions are GREATEST & LEAST. Group Functions returns results based upon groups of rows rather than one result per row, use group functions. They are AVG, COUNT, MAX, MIN & SUM.
6. What is TTITLE and BTITLE?
TTITLE & BTITLE are commands to control report headings & footers.
7. What is COLUMN?
COLUMN command define column headings & format data values.
8.What is BREAK?
BREAK command clarify reports by suppressing repeated values, skipping lines & allowing for controlled break points.
9. What is COMPUTE?
command control computations on subsets created by the BREAK command.
10. What is SET?
SET command changes the system variables affecting the report environment.
11. What is SPOOL?
SPOOL command creates a print file of the report.
12.What is a JOIN?
JOIN is the form of SELECT command that combines info from two or more tables.
Types of Joins are Simple (Equijoin & Non-Equijoin), Outer & Self join.
Equijoin returns rows from two or more tables joined together based upon a equality condition in the WHERE clause.
Non-Equijoin returns rows from two or more tables based upon a relationship other than the equality condition in the WHERE clause.
Outer Join combines two or more tables returning those rows from one table that have no direct match in the other table.
Self Join joins a table to itself as though it were two separate tables.
13. What is Union?
Union is the product of two or more tables.
14. What is Intersect?
Intersect is the product of two tables listing only the matching rows.
15. What is Minus?
Minus is the product of two tables listing only the non-matching rows.
16.What is Correlated Subquery?
Correlated Subquery is a subquery that is evaluated once for each row processed by the parent statement. Parent statement can be Select, Update or Delete. Use CRSQ to answer multipart questions whose answer depends on the value in each row processed by parent statement.
17. What is Multiple columns?
Multiple columns can be returned from a Nested Subquery.
18.What is Sequences?
Sequences are used for generating sequence numbers without any overhead of locking. Drawback is that after generating a sequence number if the transaction is rolled back, then that sequence number is lost.
19.What is Synonyms?
Synonyms is the alias name for table, views, sequences & procedures and are created for reasons of Security and Convenience.
Two levels are Public - created by DBA & accessible to all the users. Private - Accessible to creator only. Advantages are referencing without specifying the owner and Flexibility to customize a more meaningful naming convention.
20.What is Indexes?
Indexes are optional structures associated with tables used to speed query execution and/or guarantee uniqueness. Create an index if there are frequent retrieval of fewer than 10-15% of the rows in a large table and columns are referenced frequently in the WHERE clause. Implied tradeoff is query speed vs. update speed. Oracle automatically update indexes. Concatenated index max. is 16 columns.
21.What is Data types?
Max. columns in a table is 255. Max. Char size is 255, Long is 64K & Number is 38 digits.
Cannot Query on a long column.
Char, Varchar2 Max. size is 2000 & default is 1 byte.
Number(p,s) p is precision range 1 to 38, s is scale -84 to 127.
Long Character data of variable length upto 2GB.
Date Range from Jan 4712 BC to Dec 4712 AD.
Raw Stores Binary data (Graphics Image & Digitized Sound). Max. is 255 bytes.
Mslabel Binary format of an OS label. Used primarily with Trusted Oracle.
22. Order of SQL statement execution?
Where clause, Group By clause, Having clause, Order By clause & Select.
23.What is Transaction?
Transaction is defined as all changes made to the database between successive commits.
24.What is Commit?
Commit is an event that attempts to make data in the database identical to the data in the form. It involves writing or posting data to the database and committing data to the database. Forms check the validity of the data in fields and records during a commit. Validity check are uniqueness, consistency and db restrictions.
25.What is Posting?
Posting is an event that writes Inserts, Updates & Deletes in the forms to the database but not committing these transactions to the database.
26.What is Rollback?
Rollback causes work in the current transaction to be undone.
27.What is Savepoint?
Savepoint is a point within a particular transaction to which you may rollback without rolling back the entire transaction.
28. What is Set Transaction?
Set Transaction is to establish properties for the current transaction.
29.What is Locking?
Locking are mechanisms intended to prevent destructive interaction between users accessing data. Locks are used to achieve.
30. What is Consistency?
Consistency : Assures users that the data they are changing or viewing is not changed until the are thro' with it.
31.What is SQL Integrity?
Assures database data and structures reflects all changes made to them in the correct sequence. Locks ensure data integrity and maximum concurrent access to data. Commit statement releases all locks. Types of locks are given below.
Data Locks protects data i.e. Table or Row lock.
Dictionary Locks protects the structure of database object i.e. ensures table's structure does not change for the duration of the transaction.
Internal Locks & Latches protects the internal database structures. They are automatic.
Exclusive Lock allows queries on locked table but no other activity is allowed.
Share Lock allows concurrent queries but prohibits updates to the locked tables.
Row Share allows concurrent access to the locked table but prohibits for a exclusive table lock.
Row Exclusive same as Row Share but prohibits locking in shared mode.
Shared Row Exclusive locks the whole table and allows users to look at rows in the table but prohibit others from locking the table in share or updating them.
Share Update are synonymous with Row Share.
32.What is SQL Deadlock?
Deadlock is a unique situation in a multi user system that causes two or more users to wait indefinitely for a locked resource. First user needs a resource locked by the second user and the second user needs a resource locked by the first user. To avoid dead locks, avoid using exclusive table lock and if using, use it in the same sequence and use Commit frequently to release locks.
33. What is Mutating SQL Table?
Mutating Table is a table that is currently being modified by an Insert, Update or Delete statement. Constraining Table is a table that a triggering statement might need to read either directly for a SQL statement or indirectly for a declarative Referential Integrity constraints. Pseudo Columns behaves like a column in a table but are not actually stored in the table. E.g. Currval, Nextval, Rowid, Rownum, Level etc.
34.What is SQL*Loader?
SQL*Loader is a product for moving data in external files into tables in an Oracle database. To load data from external files into an Oracle database, two types of input must be provided to SQL*Loader : the data itself and the control file. The control file describes the data to be loaded. It describes the Names and format of the data files, Specifications for loading data and the Data to be loaded (optional). Invoking the loader sqlload username/password controlfilename <options>.
35.The most important DDL statements in SQL are?
CREATE TABLE - creates a new database table
ALTER TABLE - alters (changes) a database table
DROP TABLE - deletes a database table
CREATE INDEX - creates an index (search key)
DROP INDEX - deletes an index
36. Operators used in SELECT statements are?
= Equal
<> or != Not equal
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
BETWEEN Between an inclusive range
LIKE Search for a pattern
37.SELECT statements in SQL?
SELECT column_name(s) FROM table_name
SELECT DISTINCT column_name(s) FROM table_name
SELECT column FROM table WHERE column operator value
SELECT column FROM table WHERE column LIKE pattern
SELECT column,SUM(column) FROM table GROUP BY column
SELECT column,SUM(column) FROM table GROUP BY column HAVING SUM(column) condition value
Note that single quotes around text values and numeric values should not be enclosed in quotes. Double quotes may be acceptable in some databases.
38.The SELECT INTO Statement is most often used to create backup copies of tables or for archiving records?
SELECT column_name(s) INTO newtable [IN externaldatabase] FROM source
SELECT column_name(s) INTO newtable [IN externaldatabase] FROM source WHERE column_name operator value
39.The INSERT INTO Statements in SQL?
INSERT INTO table_name VALUES (value1, value2,....)
INSERT INTO table_name (column1, column2,...) VALUES (value1, value2,....)
40. The Update Statement in SQL.?
UPDATE table_name SET column_name = new_value WHERE column_name = some_value
41. The Delete Statements in SQL.?
DELETE FROM table_name WHERE column_name = some_value
Delete All Rows:
DELETE FROM table_name or DELETE * FROM table_name
41. Sort the Rows in SQL.?
Sort the Rows:
SELECT column1, column2, ... FROM table_name ORDER BY columnX, columnY, ..
SELECT column1, column2, ... FROM table_name ORDER BY columnX DESC
SELECT column1, column2, ... FROM table_name ORDER BY columnX DESC, columnY ASC
42.The IN operator may be used if you know the exact value you want to return for at least one of the columns.?
SELECT column_name FROM table_name WHERE column_name IN (value1,value2,..)
43. BETWEEN ... AND operators in SQL.?
SELECT column_name FROM table_name WHERE column_name BETWEEN value1 AND value2 The values can be numbers, text, or dates.
44.What is the use of CASCADE CONSTRAINTS?
When this clause is used with the DROP command, a parent table can be dropped even when a child table exists.
Oracle SQL & PL/SQL
45.What Is SQL?
SQL (pronounced as the letters S-Q-L or as sequel) is an abbreviation for Structured Query Language. SQL is a language designed specifically for communicating with databases. SQL is designed to do one thing and do it well—provide you with a simple and efficient way to read and write data from a database.
46.Which command displays the SQL command in the SQL buffer, and then executes it?
RUN
47.What is the difference between Truncate & Drop?
48.Explain SQL Having?
49.Difference between SQL Having & Where?
50.Difference between SQL IN/SQL Exists?
51.Difference between SQL NOT IN/SQL NOT Exists?
52.Difference between SQL UNION/SQL UNION ALL?
53.Explain SQL TOP.
54.How to delete duplicate records in a table?
55.How to find duplicate records with the number they are duplicated?
SELECT Id, count (*) as num_records
from table
group by id
having count (*) > 1
56.What is a PRIMARY KEY?
The PRIMARY KEY is the column(s) used to uniquely identify each row of a table.
57.What is a FOREIGN KEY?
A FOREIGN KEY is one or more columns whose values are based on the PRIMARY or CANDIDATE KEY values from the database.
58.What is a UNIQUE KEY?
A UNIQUE KEY is one or more columns that must be unique for each row of the table.
59.What is the difference between UNIQUE and PRIMARY KEY?
The UNIQUE KEY column restricts entry of duplicate values but entry of NULL value is allowed. In case of PRIMARY KEY columns entry of duplicate as well as <null> value is also restricted.
60.Difference between Unique Key and Primary Key.?
61.Difference between Cast & Convert.?
62.Explain SQL Group by and give examples.?
63.How can you call a PL/SQL procedure from SQL?
By use of the EXECUTE (short form EXEC) command.
64.Which is the subset of SQL commands used to manipulate Oracle Database structures?
Data Definition Language (DDL)
65.Write a query to select the Nth highest salary from a table.?
66.Write a query to select the 2nd highest salary from a table.?
67.Write a query to select the second highest salary from a table.?
SELECT max(salary) AS salary_2
FROM emp
WHERE salary < (SELECT max(salary) AS salary_1
FROM emp)
68.Write a query to select the 5th highest salary from a table.?
SELECT min(salary) AS high5
FROM employee
WHERE salary IN(SELECT DISTINCT TOP 5 salary
FROM employee
ORDER BY salary DESC)
69.What command is used to get back the privileges offered by the GRANT command?
Revoke
70.How do you execute a host operating system command from within SQL?
By use of the exclamation point “!” (in UNIX and some other OS) or the HOST (HO) command.
71.What command is used to create a table by copying the structure of another table?
CREATE TABLE .. AS SELECT command
72.Give examples of Create Table?
73.What is the difference between Delete and Truncate command in SQL?
74.What is the difference between Delete and Truncate command in SQL?
Delete command and truncate command both will delete the data, however the truncate command can not be rolled back as delete can be. TRUNCATE is a DDL command whereas DELETE is a DML command. The delete command can be used for selected records using the where clause but with the truncate command we have to loose data. DELETE statement is a logged operation and hence takes more time then truncate.
75.How can variables be passed to a SQL routine?
By use of the & symbol. For passing in variables the numbers 1-8 can be used (&1, &2,...,&8) to pass the values after the command into the SQLPLUS session. To be prompted for a specific variable, place the ampersanded variable in the code itself: “select * from dba_tables where owner=&owner_name;” . Use of double ampersands tells SQLPLUS to resubstitute the value for each subsequent use of the variable, a single ampersand will cause a reprompt for the value unless an ACCEPT statement is used to get the value from the user.
76.What SQLPlus command is used to format output from a select?
This is best done with the COLUMN command.
77.Can Primary key is a Foreign Key on the same table?
Yes
78.You want to determine the location of identical rows in a table before attempting to place a unique index on the table, how can this be done?
Oracle tables always have one guaranteed unique column, the rowid column. If you use a min/max function against your rowid and then select against the proposed primary key you can squeeze out the rowids of the duplicate rows pretty quick. For example:
select rowid from emp e
where e.rowid > (select min(x.rowid)
from emp x
where x.emp_no = e.emp_no);
79.What is the use of the DROP option in the ALTER TABLE command?
It is used to drop constraints specified on the table.
80.What is a Cartesian product?
A Cartesian product is the result of an unrestricted join of two or more tables. The result set of a three table Cartesian product will have x * y * z number of rows where x, y, z correspond to the number of rows in each table involved in the join.
81.How do you prevent output from coming to the screen?
The SET option TERMOUT controls output to the screen. Setting TERMOUT OFF turns off screen output. This option can be shortened to TERM.
82.What is the use of CASCADE CONSTRAINTS?
When this clause is used with the DROP command, a parent table can be dropped even when a child table exists.
83.Which function is used to find the largest integer less than or equal to a specific value?
FLOOR
Consider the below DEPT and EMPLOYEE table and answer the below queries.
DEPT
DEPTNO (NOT NULL , NUMBER(2)),
DNAME (VARCHAR2(14)),
LOC (VARCHAR2(13)
EMPLOYEE
EMPNO (NOT NULL , NUMBER(4)),
ENAME (VARCHAR2(10)),
JOB (VARCHAR2(9)),
MGR (NUMBER(4)),
HIREDATE (DATE),
SAL (NUMBER(7,2)),
COMM (NUMBER(7,2)),
DEPTNO (NUMBER(2))
MGR is the EMPno of the Employee whom the Employee reports to.
DEPTNO is a foreign key.
1. List all the Employees who have at least one person reporting to them.
SELECT ENAME FROM EMPLOYEE WHERE EMPNO IN (SELECT MGR FROM EMPLOYEE);
2. List the highest salary paid for each job.
SELECT JOB, MAX(SAL) FROM EMPLOYEE GROUP BY JOB
3. In which year did most people join the company? Display the year and the number of Employees.
SELECT TO_CHAR(HIREDATE,'YYYY') "YEAR", COUNT(EMPNO) "NO. OF EMPLOYEES"
FROM EMPLOYEE
GROUP BY TO_CHAR(HIREDATE,'YYYY')
HAVING COUNT(EMPNO) = (SELECT MAX(COUNT(EMPNO))
FROM EMPLOYEE
GROUP BY TO_CHAR(HIREDATE,'YYYY'));
4. Write a correlated sub-query to list out the Employees who earn more than the average salary of their department.
SELECT ENAME,SAL
FROM EMPLOYEE E
WHERE SAL > (SELECT AVG(SAL)
FROM EMPLOYEE F
WHERE E.DEPTNO = F.DEPTNO);
5. Find the nth maximum salary.
SELECT ENAME, SAL
FROM EMPLOYEE A
WHERE &N = (SELECT COUNT (DISTINCT(SAL))
FROM EMPLOYEE B
WHERE A.SAL<=B.SAL);
6. Select the duplicate records (Records, which are inserted, that already exist) in the EMPLOYEE table.
SELECT * FROM EMPLOYEE A
WHERE A.EMPNO IN (SELECT EMPNO
FROM EMPLOYEE
GROUP BY EMPNO
HAVING COUNT(EMPNO)>1)
AND A.ROWID!=MIN (ROWID));
7. Write a query to list the length of service of the Employees (of the form n years and m months).
SELECT ENAME "EMPLOYEE",TO_CHAR(TRUNC(MONTHS_BETWEEN(SYSDATE,HIREDATE)/12))
||' YEARS '|| TO_CHAR(TRUNC(MOD(MONTHS_BETWEEN
(SYSDATE, HIREDATE),12)))||' MONTHS ' "LENGTH OF SERVICE"
FROM EMPLOYEE;
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