Question

I need to delete partially similar rows in a table, using MySQL. Ex:

From table1 (id,color1,color2,key) content:

id,color1,color2,key
-----------------------------
1,Blue,Green,AASDDD
2,Blue,Green,JJUUYYY
3,Blue,Red,HHYYY
4,Green,Red,KKIII
5,Blue,Red,KKIIUUUU

I’d like to delete the duplicate rows in color1,color2 and get:

id,color1,color2,key
-----------------------------
1,Blue,Green,AASDDD
3,Blue,Red,HHYYY
4,Green,Red,KKIII

Something like

delete FROM table1 WHERE Exists(SELECT color1,color2 FROM table1)

What’s the best way to do this in MySQL without creating a temporary table?

(I know there are many posts about deleting duplicate rows in MySQL, but not for partially matching rows.)

Answer 1

DELETE FROM table1 
WHERE id NOT IN (SELECT min(id) 
                 FROM table1 
                 GROUP BY color1, color2)

edit

MySQL can’t delete from a table with a subquery of the same table. To work around that limitation you can do this:

DELETE FROM table1 
WHERE id NOT IN (select * from (SELECT min(id) 
                               FROM table1 
                               GROUP BY color1, color2) t)