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ORACLE Interview Questions and Answers
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(Continued from previous part...)
480. What happens if a procedure that updates a column of table X is called in a database trigger of the same table ?
Mutation of table occurs.
481. Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger ? Why ?
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.
482. How many types of database triggers can be specified on a table ? What are they ?
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.
483. What are the modes of parameters that can be passed to a procedure ?
IN,OUT,IN-OUT parameters.
484. Where the Pre_defined_exceptions are stored ?
In the standard package.
Procedures, Functions & Packages ;
485. Write the order of precedence for validation of a column in a table ?
I. done using Database triggers.
ii. done using Integarity Constraints.?
I & ii.
486. Give the structure of the function ?
FUNCTION name (argument list .....) Return datatype is
local variable declarations
Begin
executable statements
Exception
execution handlers
End;
487. Explain how procedures and functions are called in a PL/SQL block ?
Function is called as part of an expression.
sal := calculate_sal ('a822');
procedure is called as a PL/SQL statement
calculate_bonus ('A822');
488. What are advantages fo Stored Procedures?
Extensibility,Modularity, Reusability, Maintainability and one time compilation.
489. What is an Exception ? What are types of Exception ?
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.
(Continued on next part...)
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