CODEWITHSUNDEEP
sqlsql-serversql-server-2005t-sqlgreatest-n-per-group
Chris
Chris

Reputation: 28064

SQL server select distinct rows using most recent value only

I have a table that has the following columns

Some of the data may look like this:

1, 1, 'EmailPreference', 'Text', 1/1/2010
2, 1, 'EmailPreference', 'Html', 1/3/2010
3, 1, 'EmailPreference', 'Text', 1/10/2010
4, 2, 'EmailPreference', 'Text', 1/2/2010
5, 2, 'EmailPreference', 'Html', 1/8/2010

I'd like to run a query that pulls the most recent value of the AttributeValue column for each distinct ForeignKeyId andAttributeName, using the Created column to determine the most recent value. Example output would be:

ForeignKeyId AttributeName    AttributeValue Created
-------------------------------------------------------
1           'EmailPreference' 'Text'         1/10/2010
2           'EmailPreference' 'Html'         1/8/2010

How can I do this using SQL Server 2005?

Upvotes: 19

Views: 39380

Answers (2)

SQLMenace
SQLMenace

Reputation: 135011

One way

select t1.* from (select ForeignKeyId,AttributeName, max(Created) AS MaxCreated
from  YourTable
group by ForeignKeyId,AttributeName) t2
join YourTable t1 on t2.ForeignKeyId = t1.ForeignKeyId
and t2.AttributeName = t1.AttributeName
and t2.MaxCreated = t1.Created

See also Including an Aggregated Column's Related Values for 5 different ways to do this kind of query

Upvotes: 24

OMG Ponies
OMG Ponies

Reputation: 332571

Use:

SELECT x.foreignkeyid,
       x.attributename,
       x.attributevalue,
       x.created
  FROM (SELECT t.foreignkeyid,
               t.attributename,
               t.attributevalue,
               t.created,
               ROW_NUMBER() OVER (PARTITION BY t.foreignkeyid, t.attributename 
                                      ORDER BY t.created DESC) AS rank
          FROM TABLE t) x
 WHERE x.rank = 1

Using a CTE:

WITH summary AS (
    SELECT t.foreignkeyid,
           t.attributename,
           t.attributevalue,
           t.created,
           ROW_NUMBER() OVER (PARTITION BY t.foreignkeyid, t.attributename 
                                  ORDER BY t.created DESC) AS rank
      FROM TABLE t)
SELECT x.foreignkeyid,
       x.attributename,
       x.attributevalue,
       x.created
  FROM summary x
 WHERE x.rank = 1

Also:

SELECT t.foreignkeyid,
       t.attributename,
       t.attributevalue,
       t.created
  FROM TABLE t
  JOIN (SELECT x.foreignkeyid,
               x.attributename,
               MAX(x.created) AS max_created
          FROM TABLE x
      GROUP BY x.foreignkeyid, x.attributename) y ON y.foreignkeyid = t.foreignkeyid
                                                 AND y.attributename = t.attributename
                                                 AND y.max_created = t.created

Upvotes: 10

Related Questions