如何在MySQL中获得2列的所有不同组合 [英] How to get all the distinct combinations of 2 columns in MySQL

问题描述

我有一个带有值的表t

+------+------+------+
| col1 | col2 | col3 |
+------+------+------+  
|    1 |    2 | x    |
|    1 |    3 | x    |
|    1 |    4 | x    |
|    2 |    1 | x    |
|    2 |    3 | x    |
|    2 |    4 | x    |
+------+------+------+

我需要这个结果:

+------+------+------+
| col1 | col2 | col3 |
+------+------+------+  
|    1 |    2 | x    |
|    1 |    3 | x    |
|    1 |    4 | x    |
|    2 |    3 | x    |
|    2 |    4 | x    |
+------+------+------+

注意(1,2)与(2,1)相同

Note (1,2) is same as (2,1)

推荐答案

要使用DISTINCT子句，您需要手动对前两列进行排序:

In order to use the DISTINCT clause, you need to sort the first two columns manually:

SELECT DISTINCT
    CASE WHEN (col1 < col2) THEN col1 else col2 END AS Col1,
    CASE WHEN (col1 < col2) THEN col2 else col1 END AS Col2,
    col3
FROM t

查看此SQLFiddle

这篇关于如何在MySQL中获得2列的所有不同组合的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！