IF#
Synopsis#
IF condition
  THEN statements
  [ ELSEIF condition THEN statements ]
  [ ... ]
  [ ELSE statements ]
END IF
Description#
The IF THEN statement is an optional construct to allow conditional processing
in SQL routines. Each condition  following an IF
or ELSEIF must evaluate to a boolean. The result of processing the expression
must result in a boolean true value to process the statements in the THEN
block. A result of false results in skipping the THEN block and moving to
evaluate the next ELSEIF and ELSE blocks in order.
The ELSEIF and ELSE segments are optional.
Examples#
FUNCTION simple_if(a bigint)
  RETURNS varchar
  BEGIN
    IF a = 0 THEN
      RETURN 'zero';
    ELSEIF a = 1 THEN
      RETURN 'one';
    ELSE
      RETURN 'more than one or negative';
    END IF;
  END
Further examples of varying complexity that cover usage of the IF statement in
combination with other statements are available in the SQL routines examples
documentation.