Mysql问题集锦

You can't specify target table 't_ams_ac_if' for update in FROM clause

原SQL:
UPDATE t_a
SET c_a='B'
WHERE c_id=(
SELECT c_id
FROM t_a
WHERE c_a = 'A'
);
原因：从原表中查出数据不能直接修改
修改方法：将子查询出的结果放置到临时表中再修改原表
UPDATE t_a
SET c_a='B'
WHERE c_id=(
SELECT a.c_id FROM (
SELECT c_id
FROM t_a
WHERE c_a = 'A'
) a
);

2.You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'a WHERE c_id=1' at line
原SQL:
DELETE FROM t_a a WHERE c_id=1;
原因：
修改方法：当给欲删除数据的表起别名后需要在DELETE FROM语句之间显式声明表别名
DELETE a FROM t_a a WHERE c_id=1;