T-SQL: Selecting Column Based on MAX(Other Column)

Question

I\'m hoping there\'s a simple way to do this without using a sub-query:

Scenario: You have \"TableA\" with columns \"Key\", \"SubKey\", and \"Value\". I need to ge

Answer 1

Using a self join:

This will return all the values with subkey values that match, in case there are multiples.

SELECT a.value
  FROM TABLE a
  JOIN (SELECT MAX(t.subkey) AS max_subkey
          FROM TABLE t
         WHERE t.key = 1) b ON b.max_subkey = a.subkey
 WHERE a.key = 1

Using RANK & CTE (SQL Server 2005+):

This will return all the values with subkey values that match, in case there are multiples.

WITH summary AS (
  SELECT t.*,
         RANK() OVER(ORDER BY t.subkey DESC) AS rank
    FROM TABLE t
   WHERE t.key = 1)
SELECT s.value
  FROM summary s
 WHERE s.rank = 1

Using ROW_NUMBER & CTE (SQL Server 2005+):

This will return one row, even if there are more than one with the same subkey value...

WITH summary AS (
  SELECT t.*,
         ROW_NUMBER() OVER(ORDER BY t.subkey DESC) AS rank
    FROM TABLE t
   WHERE t.key = 1)
SELECT s.value
  FROM summary s
 WHERE s.rank = 1

Using TOP:

This will return one row, even if there are more than one with the same subkey value...

  SELECT TOP 1
         t.value
    FROM TABLE t
   WHERE t.key = 1
ORDER BY t.subkey DESC