mysql - 选择两个值相等的几个 id

Question

例如我有这两个表

+----+----+----+----+   +----+----+----+----+
| id | c1 | c2 | c3 |   | id | c1 | c2 | c4 |
+----+----+----+----+   +----+----+----+----+
| 10 | 50 | 55 | 20 |   | 20 | 50 | 55 | 24 |
+----+----+----+----+   +----+----+----+----+
| 12 | 15 | 10 | 70 |   | 26 | 21 | 82 | 11 |
+----+----+----+----+   +----+----+----+----+
| 18 | 15 | 10 | 88 |   | 27 | 15 | 10 | 13 |
+----+----+----+----+   +----+----+----+----+

我想得到两个具有相同 c1 和 c2 值的 id，对于上面的例子我必须得到这个输出:

+----+----+
| id | id |
+----+----+
| 10 | 20 |
+----+----+
| 12 | 27 |
+----+----+
| 12 | 18 |
+----+----+
| 18 | 27 |
+----+----+

Answer 1

你只需要像这样连接两个表:

SELECT DISTINCT t1.id as id1, t2.id as id2
FROM table1 AS t1
INNER JOIN table2 AS t2 ON t1.c1 = t2.c1 AND t1.c2 = t2.c2
UNION
SELECT DISTINCT t1.id as id1, t2.id as id2
FROM table1 AS t1
INNER JOIN table1 AS t2  ON t1.c1 = t2.c1 AND t1.c2 = t2.c2
                        AND t1.id != t2.id
UNION
SELECT DISTINCT t1.id as id1, t2.id as id2
FROM table2 AS t1
INNER JOIN table2 AS t2  ON t1.c1 = t2.c1 AND t1.c2 = t2.c2
                        AND t1.id != t2.id;

Results :

| id1 | id2 |
|-----|-----|
|  10 |  20 |
|  12 |  27 |
|  18 |  27 |
|  18 |  12 |
|  12 |  18 |