IF search_condition THEN statement(s) [ELSEIF search_condition THEN statement(s)] ... [ELSE statement(s)] END IF
          IF implements a basic conditional
          construct. If the search_condition
          evaluates to true, the corresponding SQL statement is
          executed. If no search_condition matches,
          the statement in the ELSE clause is
          executed.
        
          Please note that there is also an IF()
          function. See Secção 6.3.1.4, “Funções de Fluxo de Controle”.
        
This is a translation of the MySQL Reference Manual that can be found at dev.mysql.com. The original Reference Manual is in English, and this translation is not necessarily as up to date as the English version.

