SQL Group By and min (MySQL)

Question

I have the following SQL:

select code, distance from places;    

The output is below:

CODE    DISTANCE            LOCATION
         


        

Answer 1

You did not say your DBMS. The following solutions are for SQL Server.

WITH D AS (
   SELECT code, distance, location,
      Row_Number() OVER (PARTITION BY code ORDER BY distance) Seq
   FROM places
)
SELECT *
FROM D
WHERE Seq = 1

If you have a table with unique Codes, and an index in your Places table on [Code, Distance] then a CROSS APPLY solution could be better:

SELECT
   X.*
FROM
   Codes C
   CROSS APPLY (
      SELECT TOP 1 *
      FROM Places P
      WHERE C.Code = P.Code
      ORDER BY P.Distance
   ) X

I cannot work on a solution for mysql unti much later.

P.S. You cannot rely on insertion order. Do not try!