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IF


Provides conditional execution based on the truth value of a conditional expression.



Usage

Procedural.

Description

The IF statement allows a sequence of procedural-sql-statements to be conditionally executed depending on the truth value of a search-condition.

For a list of procedural-sql-statements, see Procedural SQL Statements.

All of the predicates supported by Mimer SQL may be used in the search-condition, see Predicates.

In a basic IF statement, the sequence of procedural-sql-statements in the THEN clause will be executed if search-condition evaluates to true, otherwise the sequence of procedural-sql-statements in the ELSE clause will be executed.

One or more IF statements can be nested by using the ELSEIF clause in place of an ELSE clause containing another IF statement.

Language Elements

search-condition, see Search Conditions.

Notes

If the search-condition equals NULL or directly includes the NULL value, it evaluates to unknown and its treated as false. If it is required that the conditional expression test for the NULL value, then the correct behavior is achieved by using the IS NULL predicate, see The NULL Predicate.

Example

 if  X > 50 then
     SET X = 50;
     SET Y = 1;
 else
     SET Y = 0;
 end if;
 
 declare bookExists boolean;
 
 set bookExists = exists (select * from books where ... );
 
 if  bookExists then
      ...
 end if;
 
 declare bookTitle row(ISBN varchar(20), Title varchar(50));
 ...
 
 if  booktitle = ('0-201-43328-1','JDBC API Tutorial and Reference') then
      ...
 end if;
 

For more information, see the Mimer SQL Programmer's Manual, Conditional Execution Using IF.

Standard Compliance

Standard
Compliance
Comments
SQL-2011
Features outside core
Feature P002, "Computational completeness".


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