kontrollera om kolumnen finns före ALTER TABLE -- mysql

Eftersom mysql-kontrollsatser (t.ex. "IF") bara fungerar i lagrade procedurer, kan en temporär skapas och köras:

DROP PROCEDURE IF EXISTS add_version_to_actor;

DELIMITER $$

CREATE DEFINER=CURRENT_USER PROCEDURE add_version_to_actor ( ) 
BEGIN
DECLARE colName TEXT;
SELECT column_name INTO colName
FROM information_schema.columns 
WHERE table_schema = 'connjur'
    AND table_name = 'actor'
AND column_name = 'version';

IF colName is null THEN 
    ALTER TABLE  actor ADD  version TINYINT NOT NULL DEFAULT  '1' COMMENT  'code version of actor when stored';
END IF; 
END$$

DELIMITER ;

CALL add_version_to_actor;

DROP PROCEDURE add_version_to_actor;