mysql在增加列前进行判断该列是否存在_MySQL

mysql在增加列前进行判断该列是否存在

Mysql没有直接的语法可以在增加列前进行判断该列是否存在，需要写一个存储过程完成同样任务，

下面例子是：在T_DT_HOMEWORK表中增加一列RECOMMEND_RECORD列

1create procedure add_col_homework() BEGIN 2IF EXISTS (SELECT column_name FROM information_schema.columns WHERE column_name = 'T_DT_HOMEWORK' AND column_name = 'RECOMMEND_RECORD')3THEN 4   ALTER TABLE `T_DT_HOMEWORK`  DROP COLUMN `RECOMMEND_RECORD`;5END IF; 6   ALTER TABLE `T_DT_HOMEWORK` ADD COLUMN  `RECOMMEND_RECORD`  varchar(20) CHARACTER   SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL AFTER `RECOMMEND_ORG_CODE`;7END;89drop procedure if exists add_col_homework;