Signal an exception condition.

 

Syntax

 

<signal statement> ::= SIGNAL <character string literal>

 

 

Usage

 

The SIGNAL statement is used to throw an exception with the message specified by the character string literal.

 

 

Examples

 

1)

The following example throws an exception:



 


SIGNAL 'Dummy Exception.';



 

2)

The following example shows the SIGNAL statement used in a conditional computation:



 


DECLARE v1, v2 DOUBLE PRECISION;


SET v1 = RAND;


SET v2 = RAND;


IF ( v1 = v2 ) THEN




SIGNAL 'The values are equal.';



  ELSE


SIGNAL 'The values are different.';




END IF;



 

3) The following example shows the SIGNAL statement used in the CATCH clause of a TRY statement:

 


START TRANSACTION;


TRY




DROP TABLE garbage;


COMMIT;




CATCH POSITION( 'Unable to open table' IN ERROR_MESSAGE ) <> 0




ROLLBACK;


SIGNAL 'The table couldn''t be dropped.' || CHR(13) || 'The transaction was rolled back.';




END;



 

 


 

Conformance

 

SQL:2003 standard

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SQL/PSM Feature P002-14 "SIGNAL statement"