mysql - Mysql使用多个条件选择数据

Question

我有一张像

id   fid
20    53
23    53
53    53

在这里，当我的情况类似于时，我需要返回 true，.. where fid=53 and id in(20,23,53) 并且我需要在 时返回 false ....where fid=53 and id in(20,24,53)。但上述条件不满足我的要求。两个查询返回相同的值（true）。请帮助我继续前进。

Answer 1

我相信您要求的是查询找到与所有值 20、23、53 关联的 fid，如果没有，则查询不会返回该 fid。

SQL 中有两种常见的解决方案。

首先是我为 MySQL 推荐的一个：

SELECT t1.fid
FROM mytable t1
JOIN mytable t2 ON t1.fid = t2.fid
JOIN mytable t3 ON t1.fid = t2.fid
WHERE (t1.id, t2.id, t3.id) = (20,23,53);

这是另一个使用 group by 而不是自连接的解决方案，但在 MySQL 中往往表现更差：

SELECT t.fid
FROM mytable t
WHERE t.id IN (20,23,53)
GROUP BY t.fid
HAVING COUNT(*) = 3;

Answer 2

也许是一个子查询？

SELECT id, fid FROM table
WHERE fid = 53 AND
id IN ( SELECT id FROM table WHERE id IN(20,24,53))

Answer 3

According to your example conditions, its not possible with a single query :(. since where fid=53 and id in(20,23,53) return true for fid=53 and id =20,53 Similarly, where fid=53 and id in(20,24,53) is false for fid=53 and id =20,53

the only difference is about id=23 and id=24. So you can do it with two difference query. But sometimes they will return true and false for same data.

I think you need to think about your question once again.