selecting a column based on a minimum value of another column

Question

I have the following table.

test_type |  brand  | model  | band | firmware_version | avg_throughput
-----------+---------+--------+------+-----------------+-         


        

Answer 1

In standard SQL this can be done using a window function

select test_type, model, firmware_version, avg_throughput
from (
  select test_type, model, firmware_version, avg_throughput, 
         min(firmware_version) over (partition by test_type, model) as min_firmware
  from temp_table
) t
where firmware_version = min_firmware;

Postgres however has the distinct on operator which is usually faster than the corresponding solution with a window function:

select distinct on (test_type, model) 
       test_type, model, firmware_version, avg_throughput
from temp_table
order by test_type, model, firmware_version;

SQLFiddle example: http://sqlfiddle.com/#!15/563bd/1