MySQL SELECT unique column where other column is max

Question

I have table like this

  id     |     serial_num     |      version     | .....
  1      |         1          |          1       | .....
  2      |         2         


        

Answer 1

You can use a subquery to find the max values and then join back to your table:

select t1.id,
  t1.serial_num,
  t1.version
from yourtable t1
inner join
(
  select serial_num, 
    max(version) version
  from yourtable
  group by serial_num
) t2
  on t1.serial_num = t2.serial_num
  and t1.version = t2.version

See SQL Fiddle with Demo

Result:

| ID | SERIAL_NUM | VERSION |
-----------------------------
|  1 |          1 |       1 |
|  3 |          2 |       2 |
|  4 |          3 |       1 |
|  5 |          4 |       1 |
|  8 |          5 |       3 |