Question

Here’s what my table TheTable looks like

ColA  | ColB  | ColC
------+-------+------
abc   | 2005  | item7
abc   | 2010  | item3
def   | 2009  | item2
def   | 2010  | item4
def   | 2011  | item5
def   | 2012  | item1

And I want to write a query to return this result:

ColA  | ColB  | ColC
------+-------+------
abc   | 2010  | item3
def   | 2012  | item1

I ended up with:

SELECT TheTable.ColA,TheTable.ColB,TheTable.ColC
FROM TheTable,(SELECT ColA a,MAX(ColB) b FROM TheTable GROUP BY ColA) t
WHERE t.a=TheTable.ColA AND t.b=TheTable.ColB

But I’m not sure this kind of nested query is very efficient. So the question is, is there a better way?

Answer 1

WITH OrderedTable AS
(
    SELECT ColA, ColB, ColC,
        ROW_NUMBER() OVER (PARTITION BY ColA ORDER BY ColB DESC) AS Row
    FROM TheTable
)
SELECT ColA, ColB, ColC FROM OrderedTable WHERE Row = 1