MySQL在IN条件下使用UNION子查询删除

Question

我遇到了一个奇怪的SQL错误。 最后一个查询不起作用。 当然，我可以将DELETE分为三个查询，但是我真的很奇怪，为什么MySQL不允许我这样做。

一个小例子：

(SELECT id FROM stairs WHERE building = 123)
UNION
(SELECT id FROM lift WHERE building = 123)
UNION
(SELECT id FROM qrcodeid WHERE building = 123)

作品！

DELETE FROM startpoint WHERE id IN (SELECT id FROM stairs WHERE building = 123)

也可以！

而

DELETE FROM startpoint WHERE id IN (
    (SELECT id FROM stairs WHERE building = 123)
    UNION
    (SELECT id FROM lift WHERE building = 123)
    UNION
    (SELECT id FROM qrcodeid WHERE building = 123)
)

引发错误

＃1064-您的SQL语法有误； 检查与您的MySQL服务器版本相对应的手册以获取正确的语法，以在第3行的'UNION（SELECT ID FROM Lift WHERE building = 123）UNION（SELECT id FROM qrc'）附近使用

任何线索？

Answer 1

试试这个版本：

DELETE FROM startpoint
    WHERE id IN (select *
                 from ((SELECT id FROM stairs WHERE building = 123)
                       UNION
                      (SELECT id FROM lift WHERE building = 123)
                       UNION
                      (SELECT id FROM qrcodeid WHERE building = 123)
                )

我认为这个问题是关于子查询定义的不可思议的问题。 子查询是select语句，而union则是select语句的结合。

编辑：

实际上，如果您想提高效率，则根本不会使用这种方法。 我只是试图显示如何解决该错误。 更好的解决方案是：

DELETE sp FROM startpoint sp
    WHERE EXISTS (select 1 from stairs s where s.building = 123 and s.id = sp.id) or
          EXISTS (select 1 from lift l where l.building = 123 and l.id = sp.id) or
          EXISTS (select 1 from qrcodeid q where q.building = 123 and q.id = sp.id);

建议在stairs(id, building) ， lift(id, building)和qrcodeid(id, building) 。

Answer 2

试试那个SQL

DELETE FROM startpoint WHERE id IN (
SELECT id FROM stairs WHERE building = 123
UNION
SELECT id FROM lift WHERE building = 123
UNION
SELECT id FROM qrcodeid WHERE building = 123)