Question

鉴于MySQL 5.0中的表：

clients
=======
id  int

users
=====
id         int
client_id  int
is_primary tinyint

客户端可以有很多用户。我想更新users.is_primary = 1只针对最小的users.id per users.client_id

例如，给定这些用户：

users
id   client_id    is_primary
============================
1    1            0
2    1            0
3    2            0
4    2            0
5    3            0

我想最终：

users
id   client_id    is_primary
============================
1    1            1
2    1            0
3    2            1
4    2            0
5    3            1

有没有办法编写更新语句来执行此操作？

Answer 1

update users 
set is_primary = 1
where id in (select * from (select min(id) from users group by client_id) as t)

Answer 2

或者你应该可以像这样使用连接：

UPDATE users
  INNER JOIN (
    SELECT MIN(id) AS id
    FROM users
    GROUP BY client_id
  ) m ON users.id = m.id
SET users.is_primary = 1

sql只更新最早的多对一关联

2 个答案: