Question

I have two related tables.

Table 1:
recordid | OrderNumber | MobileNumber
       1 | 1234        | 9999999999
       2 | 1234        | 9888888888
       3 | 1234        | 9777777777
       4 | 5433        | 9666666666
       5 | 1444        | 9555555555
       6 | 1444        | 9444444444
       7 | 1544        | 9333333333
       8 | 1632        | 9222222222


Table 2
recordid | modifiedon
       1 | 15/1/2013
       2 | 17/1/2013 
       3 | 13/1/2013
       4 | 10/1/2013
       5 | 16/1/2013
       6 | 01/1/2013 
       7 | 09/1/2013
       8 | 08/1/2013

what i want to do is get a unique set of OrderNumber and their corresponding MobileNumbers. If there is are more than one record for one OrderNumber, then the query should get OrderNumber and MobileNumber of the latest modified record.

So basically i should get the following result.

OrderNumber | MobileNumber
1234        | 9888888888
5433        | 9666666666
1444        | 9555555555
1544        | 9333333333
1632        | 9222222222

i have tried

select OrderNumber, MobileNumber from Table1 
where OrderNumber in 
(
   Select Distinct table1. rderNumber, table2.ModifiedOn 
   from Table1, Table2 
   group by table2.ModifiedOn desc
) 

This is urgent and I would be very greatly to receive quick responses.

Answer 1

It’s easier with a CTE and ROW_NUMBER:

WITH cte AS 
(SELECT t1.ordernumber, 
        t1.mobilenumber, 
        RN = Row_number() 
               OVER ( 
                 partition BY t1.ordernumber 
                 ORDER BY t2, modifiedon DESC) 
         FROM   table1 t1 
                INNER JOIN table2 t2 
                        ON t1.recordid = t2.recordid) 
SELECT ordernumber, 
       mobilenumber
FROM   cte 
WHERE  rn = 1 

Apart from that, you had a DESC after a GROUP BY.