1  IF_Control
   Executes one or more SQL statements conditionally. It then
   continues processing by executing any SQL statement that
   immediately follows the block.
 

2  Environment
   You can use the IF control statement in a compound statement:

   o  In interactive SQL

   o  Embedded in host language programs to be precompiled

   o  As part of a procedure in an SQL module

   o  In dynamic SQL as a statement to be dynamically executed
 

2  Format

 if-statement =
 
 -----> IF predicate THEN --+-> compound-use-statement -+--------+
                            +------------ <-------------+        |
 +---------------------------------------------------------------+
 ++-+--------------------------------------------------------+-+-+
  | +-> ELSEIF predicate THEN -+-> compound-use-statement -+-+ | |
  |                            +------------ <-------------+   | |
  +---------------------------- <------------------------------+ |
 +---------------------------------------------------------------+
 +--+----------------------------------------+--> END IF --------->
    +-> ELSE --+-> compound-use-statement -+-+
               +------------ <-------------+
 

 

2  Arguments
 

3  compound-use-statement

   See the Compound_Statement HELP topic for a description of the
   SQL statements that are valid in a compound statement.
 

3  END_IF

   Marks the end of an IF statement. Every IF statement must end
   with the END IF clause.
 

3  ELSE_compound_use_statement

   Executes one or more SQL statements associated with the ELSE
   clause but only when the value of the IF and ELSEIF predicates
   evaluate to FALSE or UNKNOWN.
 

3  ELSEIF_THEN

   If the ELSEIF predicate evaluates to TRUE, SQL executes the SQL
   statements in the THEN clause. If the ELSEIF predicate does not
   evaluate to TRUE, SQL evaluates the predicates in any subsequent
   ELSEIF or ELSE clauses.
 

3  IF_THEN

   Executes one or more SQL statements in an IF . . . END IF block
   only when the value of an IF predicate evaluates to TRUE. A
   predicate, also called a conditional expression, specifies a
   condition that SQL evaluates to TRUE, FALSE, or UNKNOWN. If
   the predicate evaluates to TRUE, SQL executes the statement in
   the THEN clause. If the predicate does not evaluate to TRUE,
   SQL evaluates the predicate in any ELSEIF clauses. If the IF
   statement contains no ELSEIF clauses, SQL executes any statements
   in the ELSE clause.
 

3  predicate

   See the Predicates HELP topic for more information on predicates.
 

2  Examples

   Example 1: Using an IF control statement

   IF (SELECT COUNT (*) FROM STUDENTS
              WHERE CLASS = :CLASS_NUM)
        > 30

      THEN
         SET :MSG = 'Class is too large.';
      ELSE
         SET :MSG = 'Class size is O.K.';

   END IF;