获取两列相同表之间的出现次数

Question

我在如何获取MySQL中两列之间的值出现次数方面存在问题。

getdelim

我如何能够获得两列之间的出现次数，如下所示？

id1 col1 col2
2    5      3
3    3      4
4    2      1
5    1      3
6    null   2

Answer 1

您可以count列，然后应用SELECT val, COUNT(*) AS occurrence FROM (SELECT col1 AS val FROM mytable UNION ALL SELECT col2 AS val FROM mytable) x GROUP BY val ORDER BY occurrence DESC 聚合函数：

{=./}