Selecting distinct pair mysql

问题

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

For example if my table is

A  B

1  2
3  4
1  2
4  5

The output should be

A  B
1  2

A. Select Distinct A,B from table

selects all the values in the table.

B. Select Distinct (A,B) from table

tells me that Distinct function can take only one value.

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

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

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

回答1:

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

来源：https://stackoverflow.com/questions/12013900/selecting-distinct-pair-mysql