Question

I have a query that has the following

DATE                    ID              Name
---                     ------------    -----------
2012-02-07 11:24:53.000 00001-KK-12 Smith, JEN  
2011-12-28 00:00:00.000 00001-KK-12 Bearson, Matt   
2012-02-13 10:38:18.000 00003-KJ-12 Wick, Julian    

What I need to do is to get the latest date for a given ID and then show the results

So in this case, it would be:

DATE                    ID              Name
---                     ------------    -----------
2012-02-07 11:24:53.000 00001-KK-12 Smith, JEN  
2012-02-13 10:38:18.000 00003-KJ-12 Wick, Julian    

I tried to use the Top(1) with a group by on ID based but was not successful

Answer 1

There are several ways to do this. One way is to use row_number. Its useful if there’s a possibility that there’s a tie on date and you want to arbitrarily pick one.

WITH CTE AS (
SELECT 
   row_number() over (partition by id order by date desc) rn,
   date,
   id,
   name

FROM
   table)
SELECT date,
       id,
       name
FROM CTE WHERE RN = 1

Another option is to use an ANTI JOIN (no aggregates no CTE) as follows but will return multiple results if there’s a tie for first for a given ID.

   SELECT 
      t.date,
      t.id,
      t.name
   FROM
      table t
      LEFT JOIN table t1
      WHERE t.Id = t1.id
            and t.Date < t1.Date
   WHERE
       t1.Date is null