Use of GROUP BY twice in MySQL

Question

My table looks like this.

Location    Head    Id  IntTime
1           AMD     1   1
2           INTC    3   3
3           AMD     2   2
4           INTC    4         


        

Answer 1

Use UNION syntax?

(SELECT Location, Head, Id, MIN(IntTime) FROM test 
GROUP BY Id)
UNION
(SELECT Location, Head, Id, MIN(IntTime) FROM test2 
GROUP BY Head)