Question

我有2个表：edges和users

edges（约束：id1＆lt; id2）：

id1
name1
id2
name2

users：

id
name

我想获得只有edge（id1，name1，id2，name2）的结果集，以便BOTH id1和id2在users表中。这看起来很简单，但是我遇到了麻烦。我的尝试：

SELECT
   e.id1 AS id1,
   e.name1 AS name1,
   e.id2 AS id2,
   e.name2 AS name2
FROM 
   edges AS e,
   users AS u
WHERE u.id = e.id1

UNION

SELECT
   e.id1 AS id1,
   e.name1 AS name1,
   e.id2 AS id2,
   e.name2 AS name2
FROM 
   edges AS e,
   users AS u
WHERE u.id = e.id2

任何指针？

Answer 1

尝试使用两个INNER JOINS：

SELECT * FROM edges e 
JOIN users u1 ON e.name1 = u1.name 
JOIN users u2 ON e.name2 = u2.name

Answer 2

尝试一下：

select e.id1, e.name1, e.id2, e.name2 from edges e
join users u1 on e.id1 = u1.id
join users u2 on e.id2 = u2.id

Answer 3

也许是这样的：

SELECT
   e.id1 AS id1,
   e.name1 AS name1,
   e.id2 AS id2,
   e.name2 AS name2
FROM 
   edges AS e
WHERE EXISTS
  (
      SELECT
        NULL
      FROM
        users AS u
      WHERE
        u.id = e.id1
        AND u.id = e.id2
  )

MySQL顶点＆amp;边缘交叉点

3 个答案: