control_statement

control_statement ::=
   SET variable_name = value | variable_name ::= value |
      WHILE expression
       LOOP procedure_statement... END LOOP |
       LEAVE |
     IF expression THEN procedure_statement ...
        [ ELSEIF procedure_statement ... THEN] ...
          ELSE procedure_statement ... END IF |
   RETURN | RETURN SQLERROR OF cursor_name | RETURN ROW |
RETURN NOROW

Control Statement	Description
set variable = expression	Assigns a value to a variable. The value can be either a literal value (for example, 10 or 'text') or another variable. Parameters are considered as normal variables.
variable ::= expression	Alternate syntax for assigning values to variables.
while expr loop statement-list end loop	Loops while expression is true.
leave	Leaves the innermost while loop and continues executing the procedure from the next statement after the keyword end loop.
if expr then statement-list1 else statement-list2 end if	Executes statements-list1 if expression expr is true; otherwise, executes statement-list2.
if expr1 then statement-list1 elseif expr2 then statement-list2 end if	If expr1 is true, executes statement-list1. If expr2 is true, executes statement-list2. The statement can optionally contain multiple elseif statements and also an else statement.
return	Returns the current values of output parameters and exits the procedure. If a procedure has a return row statement, return behaves like return norow.
return sqlerror of cursor-name	Returns the sqlerror associated with the cursor and exits the procedure.
return row	Returns the current values of output parameters and continues execution of the procedure. Return row does not exit the procedure and return control to the caller.
return norow	Returns the end of the set and exits the procedure.