Question

I am working on a small reporting application. I have two tables

Agent Table Data

AgentID  AgentName
-------  ---------
1001     ABC
1002     XYZ
1003     POI
1004     JKL

Report Table Data

ReportID  AgentId  Labor  Mandays  Amount  SubmitDate
--------  -------  -----  -------  ------  ----------
1         1001     30     10       5000    11/12/2011
2         1001     44     18       8000    11/14/2011
3         1002     33     75       3022    11/12/2011
4         1001     10     10       1500    11/14/2011
5         1002     10     10       1800    11/14/2011
6         1001     10     10       1400    11/14/2011
7         1003     40     40       1500    11/14/2011
8         1003     40     40       1800    11/14/2011

I want to generate a report which gives us output like

ReportID  AgentId  Labor  Mandays  Amount  SubmitDate
--------  -------  -----  -------  ------  ----------
1         1001     30     10       5000    11/12/2011
3         1002     33     75       3022    11/12/2011
6         1001     10     10       1400    11/14/2011
5         1002     10     10       1800    11/14/2011
8         1003     40     40       1800    11/14/2011

Thanks in Advance

Answer 1

You didn’t mention what VERSION of SQL Server you’re using – if you’re on 2005 or newer, you can use a CTE (Common Table Expression) with the ROW_NUMBER function:

;WITH LastPerAgent AS
(
   SELECT 
       AgentID, ReportID, Labor, Mandays, Amount, SubmitDate,
       ROW_NUMBER() OVER(PARTITION BY AgentID,SubmitDate
                         ORDER BY ReportID DESC) AS 'RowNum'
   FROM dbo.Report
)
SELECT 
   AgentID, ReportID, Labor, Mandays, Amount, SubmitDate,
FROM LastPerAgent
WHERE RowNum = 1

This CTE “partitions” your data by AgentID and SubmitDate, and for each partition, the ROW_NUMBER function hands out sequential numbers, starting at 1 and ordered by ReportID DESC – so the “last” row (with the highest ReportID) for each (AgentID, SubmitDate) pair gets RowNum = 1 which is what I select from the CTE in the SELECT statement after it.

PS: this doesn’t work 100% on your input data, since you’ve not defined how to group and how to eliminate rows…. you might need to adapt this query a bit, based on your requirements…