How to remove duplicates from different columns table in sql-CodePudding

I have data in which i have duplicates but in different columns for ex :

Column A	Column B
1	2
2	1
3	4
4	3

but now my output should look like

Column A	Column B
1	2
3	4

how can i achieve this using sql query ?

CodePudding user response：

We can use a least/greatest trick here:

SELECT DISTINCT LEAST(a, b) AS a, GREATEST(a, b) AS b
FROM yourTable;

The idea is to, e.g., take the two tuples (1, 2) and (2, 1) and bring them both to (1, 2), using the LEAST() and GREATEST() functions. Then, we just retain one them using DISTINCT.