mysql添加字段,如果有则不添加

添加字段（可重复执行）：
DROP PROCEDURE IF EXISTS add_column_acl_class_copy1;
DELIMITER $$
CREATE PROCEDURE add_column_acl_class_copy1()
    BEGIN
        IF NOT EXISTS (SELECT 1  FROM information_schema.columns WHERE table_name = 'acl_class_copy1'  AND column_name = 'name')
        THEN
          ALTER TABLE acl_class_copy1 ADD COLUMN  `name`  VARCHAR(32) DEFAULT NULL  COMMENT 'testname';
        END IF;
    END$$
DELIMITER ;
-- 调用
CALL add_column_acl_class_copy1();
DROP PROCEDURE IF EXISTS add_column_acl_class_copy1;