Ora Exceptii PL SQL

8/12/2019 Ora Exceptii PL SQL

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PBD Oracle - Exceptii-1

Copyright Oracle Corporation, 1998. All rights reserved.

2323

Handling ExceptionsHandling Exceptions

23-2 Copyright Oracle Corporation, 1998. All rights reserved.

ObjectivesObjectives

After completing this lesson, you shouldbe able to do the following:

Define PL/SQL exceptions

Recognize unhandled exceptions

List and use different types of PL/SQLexception handlers

Trap unanticipated errors

Describe the effect of exceptionpropagation in nested blocks

Customize PL/SQL exception messages

After completing this lessonAfter completing this lesson,, you shouldyou should

be able tobe able to dodo the followingthe following::

Define PL/SQL exceptions

Recognize unhandled exceptions

List and use different types of PL/SQLexception handlers

Trap unanticipated errors

Describe the effect of exceptionpropagation in nested blocks

Customize PL/SQL exception messages


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Handling Exceptions with PL/SQLHandling Exceptions with PL/SQL What is an exception?

Identifier in PL/SQL that is raised duringexecution.

How is it raised?

An Oracle error occurs.

You raise it explicitly.

How do you handle it?

Trap it with a handler.

Propagate it to the calling environment.

What is an exception?

Identifier in PL/SQL that is raised duringexecution.

How is it raised?

An Oracle error occurs.

You raise it explicitly.

How do you handle it?

Trap it with a handler.

Propagate it to the calling environment.


Handling ExceptionsHandling Exceptions

TrapTrap the Exceptionthe Exception

DECLAREDECLARE

BEGINBEGIN

END;END;

ExceptionExceptionis raisedis raised

EXCEPTIONEXCEPTION

ExceptionException

is trappedis trapped

PropagatePropagate the Exceptionthe Exception

DECLAREDECLARE

BEGINBEGIN

END;END;

ExceptionExceptionis raisedis raised

EXCEPTIONEXCEPTION

Exception isException is

not trappednot trapped

ExceptionException

propagates to callingpropagates to calling

environmentenvironment


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Exception TypesException Types

Predefined Oracle Server

Non-predefined Oracle Server

User-defined

Predefined Oracle Server

Non-predefined Oracle Server

User-defined

}} ImplicitlyImplicitlyraisedraisedExplicitly raisedExplicitly raised


Trapping ExceptionsTrapping Exceptions

EXCEPTION

WHEN exception1 [OR exception2. . .] THEN

statement1;

statement2;

. . .

[WHEN exception3[OR exception4 . . .] THEN

statement1;

statement2;

. . .]

[WHEN OTHERS THEN

statement1;

statement2;

. . .]

EXCEPTION

WHEN exception1 [OR exception2. . .] THEN

statement1;

statement2;

. . .

[WHEN exception3[OR exception4 . . .] THENstatement1;

statement2;

. . .]

[WHEN OTHERS THEN

statement1;

statement2;

. . .]

SyntaxSyntaxSyntax


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Trapping Exceptions GuidelinesTrapping Exceptions Guidelines

WHEN OTHERS is the last clause.

EXCEPTION keyword starts exception-handling section.

Several exception handlers are allowed.

Only one handler is processed before

leaving the block.

WHEN OTHERS is the last clause.

EXCEPTION keyword starts exception-handling section.

Several exception handlers are allowed.

Only one handler is processed beforeleaving the block.


Trapping Predefined Oracle

Server Errors

Trapping Predefined Oracle

Server Errors

Reference the standard name in theexception-handling routine.

Sample predefined exceptions:

NO_DATA_FOUND

TOO_MANY_ROWS

INVALID_CURSOR

ZERO_DIVIDE

DUP_VAL_ON_INDEX

Reference the standard name in theexception-handling routine.

Sample predefined exceptions:

NO_DATA_FOUND

TOO_MANY_ROWS

INVALID_CURSOR

ZERO_DIVIDE

DUP_VAL_ON_INDEX


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Predefined ExceptionPredefined Exception

BEGIN SELECT ... COMMIT;

EXCEPTION

WHEN NO_DATA_FOUND THEN

statement1;

statement2;

WHEN TOO_MANY_ROWS THENstatement1;

WHEN OTHERS THEN

statement1;

statement2;

statement3;

END;

SyntaxSyntaxSyntax


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Trapping Non-Predefined OracleServer Errors

Trapping Non-Predefined OracleServer Errors

DeclareDeclare

Name theName theexceptionexception

AssociateAssociate

CodeCode thethe PRAGMAPRAGMAEXCEPTION_INITEXCEPTION_INIT

DeclarativeDeclarative SectionSection

ReferenceReference

Handle theHandle theraisedraised

exceptionexception

ExceptionException--HandlingHandling

SectionSection


DECLARE

e_products_invalidEXCEPTION;

PRAGMA EXCEPTION_INIT (

e_products_invalid, -2292);

v_message VARCHAR2(50);

BEGIN

. . .

EXCEPTION

WHEN e_products_invalid THEN

:g_message := 'Product code

specified is not valid.';

. . .

END;

DECLARE

e_products_invalidEXCEPTION;


e_products_invalid, -2292);

v_message VARCHAR2(50);

BEGIN

. . .

EXCEPTION

WHEN e_products_invalid THEN

:g_message := 'Product code

specified is not valid.';. . .

END;

Non-Predefined ErrorNon-Predefined ErrorTrap for Oracle Server error number-2292 an integrity constraint violation

Trap forTrap forOracleOracle ServerServererror numbererror number

--2292 an2292 an integrity constraint violationintegrity constraint violation

e_products_invalid EXCEPTION; 1


e_products_invalid, -2292); 2

e_products_invalid 3


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Trapping User-Defined

Exceptions

Trapping User-Defined

Exceptions

Name theName theexceptionexception

DeclareDeclare

DeclarativeDeclarative

SectionSection

RaiseRaise

Explicitly raiseExplicitly raisethe exception bythe exception by

using theusing the RAISERAISE

statementstatement

ExecutableExecutable

SectionSection

ReferenceReference

Handle theHandle theraisedraised

exceptionexception

ExceptionException--HandlingHandling

SectionSection


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User-Defined ExceptionUser-Defined Exception

[DECLARE]

e_amount_remaining EXCEPTION;

. . .BEGIN

. . .

RAISE e_amount_remaining;

. . .

EXCEPTION

WHEN e_amount_remaining THEN

:g_message := 'There is still an amount

in stock.';. . .

END;

[DECLARE]

e_amount_remaining EXCEPTION;

. . .

BEGIN

. . .

RAISE e_amount_remaining;

. . .

EXCEPTION

WHEN e_amount_remaining THEN:g_message := 'There is still an amount

in stock.';. . .

END;

ExampleExampleExample

e_amount_remaining EXCEPTION; 1

RAISE e_amount_remaining;2

e_amount_remaining

3


Functions for Trapping

Exceptions

Functions for Trapping

Exceptions

SQLCODE

Returns the numeric value for the errorcode

SQLERRM

Returns the message associated with theerror number

SQLCODE

Returns the numeric value for the errorcode

SQLERRM

Returns the message associated with theerror number


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Functions for Trapping ExceptionsFunctions for Trapping Exceptions

DECLARE

v_error_code NUMBER;

v_error_message VARCHAR2(255);

BEGIN

...

EXCEPTION

...

WHEN OTHERS THEN

ROLLBACK;

v_error_code := SQLCODE ;

v_error_message := SQLERRM ;

INSERT INTO errors VALUES(v_error_code,

v_error_message);

END;

ExampleExampleExample

SQLCODE

SQLERRM


Calling EnvironmentsCalling EnvironmentsSQL*Plus

ProcedureBuilder

Developer/2000Forms

Precompilerapplication

An enclosingPL/SQL block

Displays error number and messageto screen

Displays error number and messageto screen

Accesses error number and messagein a trigger by means of theERROR_CODE and ERROR_TEXTpackaged functions

Accesses exception number throughthe SQLCA data structure

Traps exception in exception-handling routine of enclosing block


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Propagating ExceptionsPropagating Exceptions

BEGINSELECT ...UPDATE ...IF SQL%NOTFOUND THENRAISE e_no_rows;

END IF;EXCEPTIONWHEN e_integrity THEN ...WHEN e_no_rows THEN ...

END;

DECLARE. . .e_no_rows exception;e_integrity exception;PRAGMA EXCEPTION_INIT (e_integrity, -2292);

BEGINFOR c_record IN emp_cursor LOOP

END LOOP;EXCEPTIONWHEN NO_DATA_FOUND THEN . . .WHEN TOO_MANY_ROWS THEN . . .END;

Subblocks can handleSubblocks can handle

anan exceptionexception ororpasspass

the exception to thethe exception to the

enclosing blockenclosing block..

BEGINSELECT ...UPDATE ...IF SQL%NOTFOUND THENRAISE e_no_rows;

END IF;EXCEPTIONWHEN e_integrity THEN ...WHEN e_no_rows THEN ...

END;


SummarySummary

Exception types:

Predefined Oracle Server error

Non-predefined Oracle Server error

User-defined error

Trap exceptions

Handle exceptions:

Trap the exception within the PL/SQLblock

Propagate the exception

Exception types:

Predefined Oracle Server error

Non-predefined Oracle Server error

User-defined error

Trap exceptions

Handle exceptions:

Trap the exception within the PL/SQLblock

Propagate the exception


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Practice OverviewPractice Overview

Handling named exceptions

Creating and invoking user-definedexceptions




Practice OverviewPractice Overview






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Ora Exceptii PL SQL