Syntax
------ 
IF search_condition THEN statement_list
 [ELSEIF search_condition THEN statement_list] ...
 [ELSE statement_list]
END IF;
 
Description
----------- 
IF implements a basic conditional construct. If the
search_condition
evaluates to true, the corresponding SQL statement list is
executed.
If no search_condition matches, the statement list in the
ELSE clause
is executed. Each statement_list consists of one or more
statements.
 


URL: https://mariadb.com/kb/en/if/