Question

我有下表，我希望提取所有独特的对：

+------+------+
| a    | b    |
+------+------+
|    1 |    2 |
|    1 |    3 |
|    1 |    6 |
|    1 |    9 |
|    2 |    1 |
|    2 |    3 |
|    3 |    1 |
|    3 |    2 |
|    4 |    1 |
|    6 |    5 |
+------+------+

输出应该是

+------+------+
| a    | b    |
+------+------+
|    1 |    2 |
|    1 |    3 |
|    1 |    6 |
|    1 |    9 |
|    2 |    3 |
|    6 |    5 |
+------+------+

Answer 1

试试这个：

select least(a, b) as a, greatest(a, b) as b
from table t
group by least(a, b), greatest(a, b);

这可能会产生不在原始表中的输出（例如5/6而不是6/5）。如果您想保留原始订单：

select distinct a, b
from table t
where a <= b or
      not exists (select 1 from table t2 where t2.b = t.a and t2.a = t.b);

也就是说，选择a小于或等于b或a大于b的所有对，并且不存在其他行的值顺序。

Answer 2

SELECT   a,b
FROM     tbl //your tableName
GROUP BY a,b
HAVING   COUNT(*) > 1

试试这个我的朋友

Answer 3

SELECT   *
FROM     NAMES2
GROUP BY Id,id2
HAVING   COUNT(*) > 1;

这个怎么样？

选择不同的对值mysql

3 个答案: