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(Paper) ORACLEÂ PLACEMENT PAPER (TECHNICAL-DATABASE)
PAPER: ORACLE PLACEMENT PAPER (TECHNICAL-DATABASE)
1. 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.
2. 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.
3. 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
4. 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.
5. 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.
6. 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.
7. How many types of database
triggers can be specified on a table ? What are they ?
ANS:-Insert Update Delete
Before Row, After
Row , Before Statement , After
Statement
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.
8. 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.
9. 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.
10. 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.
11. Write the order of precedence
for validation of a column in a table ?
I.
done using Database triggers.
ii. done using Integrity
Constraints.
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.
13. 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)
14. 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.
15. 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.
16. Where the
Pre_defined_exceptions are stored ? In
the standard package?
ANS:-Procedures, Functions &
Packages ;
17. What is a stored procedure ?
ANS:-A stored procedure is a
sequence of statements that perform specific function.
18. What is difference between a
PROCEDURE & FUNCTION ?
ANS:-A FUNCTION is always returns a
value using the return statement. A
PROCEDURE has no return type.
19. What are advantages for Stored
Procedures ?
ANS:-Extensibility, Modularity,
Reusability, Maintainability and one time compilation.
20. What are the modes of
parameters that can be passed to a procedure ?
ANS:- IN,OUT,IN-OUT parameters.
21. What are the two parts of a
procedure ?
ANS:- Procedure Specification and
Procedure Body.
22. Give the structure of the
procedure ?
BEGIN
Executable statements.
Exception.
exception handlers
end;
23. Give the structure of the
function ?
ANS:-FUNCTION name (argument list
.....) Return data type is local
variable declarations
Begin
executable statements
Exception
execution handlers
End;
24. 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');
25. What is
Overloading of procedures ?
ANS:-The Same procedure name is
repeated with parameters of different data types and parameters in different
positions, varying number of parameters is called overloading of procedures.
e.g. DBMS_OUTPUT put_line
26. 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.
27.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.
28. 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.
29. How packaged procedures and
functions are called from the following?
ANS:-a. Stored
procedure or anonymous block
b. an application program such a PRC *C,
PRO* COBOL
c. SQL *PLUS
a. PACKAGE NAME.PROCEDURE NAME
(parameters);
variable := PACKAGE NAME.FUNCTION NAME
(arguments);
EXEC SQL EXECUTE
b.
BEGIN
PACKAGE NAME.PROCEDURE NAME (parameters)
variable := PACKAGE NAME.FUNCTION NAME
(arguments);
END;
END EXEC;
c. EXECUTE PACKAGE NAME.PROCEDURE if the
procedures does not have any
out/in-out parameters. A function can not
be called.
30. Name the tables where
characteristics of Package, procedure and functions are stored ?
ANS:-User_objects, User_Source and
User_error.
31. what is a display item?
ANS:-Display items are similar to
text items but store only fetched or assigned values. Operators cannot navigate
to a display item or edit the value it contains.
32. What is a list item?
ANS:-It is a list of text elements.
33. What are the display styles of
list items?
ANS:-Pop list, No text Item
displayed in the list item. THE
list, No element in the list is highlighted.
34. What is a radio Group?
ANS:-Radio groups display a fixed
no of options that are mutually Exclusive . User
can select one out of n number of options.
35. How many maximum number of
radio buttons can you assign to a radio group?
ANS:-Unlimited no of radio buttons
can be assigned to a radio group
36. can you change the default
value of the radio button group at run time?
ANS:- No.
37.What triggers are associated
with the radio group?
ANS:-Only when-radio-changed
trigger associated with radio group
