mysql - 选择具有多个参数的 HAVING

Question

我有users表和regulations表。

对于每个用户，每条规定有 4 行。

例如:user_id 1 接受了所有的规定，所以他在规定表中会有这样的记录:

1. user_id = 1, regulation = 1, accepted = 1
2. user_id = 1, regulation = 2, accepted = 1
3. user_id = 1, regulation = 3, accepted = 1
4. user_id = 1, regulation = 4, accepted = 1

现在我要做的是选择接受所有规定的所有用户。

不确定我应该如何构建此查询的 HAVING 部分。

这是我的看法，但我几乎可以肯定它是错误的，此外它说它没有看到 regulations.regulation 列:

SELECT users.* FROM users 
JOIN regulations ON regulations.user_id = users.id
GROUP BY regulations.user_id
HAVING
    (regulations.regulation = 1 AND regulations.accepted = 1)
and (regulations.regulation = 2 AND regulations.accepted = 1)
and (regulations.regulation = 3 AND regulations.accepted = 1)
and (regulations.regulation = 4 AND regulations.accepted = 1)

问题:在所有 4 条规定中选择所有接受 = 1 的用户的正确方法是什么？

Answer 1

您可以按如下方式进行:

SELECT users.id FROM users 
     INNER JOIN regulations ON regulations.user_id = users.id
WHERE regulations.accepted = 1
GROUP BY users.id
HAVING count(distinct regulations.regulation) = 4

它从 users 表中选择所有 users.id，其中接受的不同规则的数量为 4。'HAVING' 子句中的 count distinct 是为了确保如果相同的规则出现两次，则只计算一次. 它不检查接受的规定是否为 1、2、3 或 4 之一。

另一种使用嵌套查询而不是内部连接来达到相同效果的选项:

SELECT * from users u
WHERE 4 = ( SELECT count(distinct regulation) 
            FROM regulations r
            WHERE r.user_id=u.id and r.accepted=1 )

最后一个(确实取决于每个法规具有不同的值)没有 WHERE 或 HAVING 子句并且没有 COUNT:

SELECT u.* from users u
   INNER JOIN regulations r1 ON r1.user_id=u.id and r1.accepted=1 and r1.regulation=1
   INNER JOIN regulations r2 ON r2.user_id=u.id and r2.accepted=1 and r2.regulation=2
   INNER JOIN regulations r3 ON r3.user_id=u.id and r3.accepted=1 and r3.regulation=3
   INNER JOIN regulations r4 ON r4.user_id=u.id and r4.accepted=1 and r4.regulation=4

另见测试:Fiddle