选择不同的对mysql [英] Selecting distinct pair mysql

问题描述

我想选择A列和B列中具有相同值的行.

I would like to select the rows that has the same values across column A and column B.

例如，如果我的桌子是

A  B

1  2
3  4
1  2
4  5

输出应为

A  B
1  2

A. Select Distinct A,B from table

选择表中的所有值.

B. Select Distinct (A,B) from table

告诉我Distinct函数只能取一个值.

tells me that Distinct function can take only one value.

C. Select A,B from table group by A,B

选择表中的所有值(类似于A).

Selects all the values in the table (Similar to A).

问题类似于选择不同的组合. 但是答案提示那行不通.

The question is similar to Selecting Distinct combinations. but the answer suggested there doesn't work.

推荐答案

您只需要具有重复项的行.您可以使用HAVING子句基于聚合函数来过滤数据的分组":

You want only the rows which have duplicates. You can use the HAVING clause to filter "groupings" of data based on aggregation functions:

SELECT   A,B
FROM     tbl
GROUP BY A,B
HAVING   COUNT(*) > 1

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