Question

Here is the code I’ve written to create a scenario:

USE tempdb
GO
IF  EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'dbo.Emp') AND type in (N'U'))
DROP TABLE Emp
GO
CREATE TABLE Emp(
EmpID Int Identity(10,1) Primary Key,
EmpGroupID Int)
GO
INSERT INTO Emp(EmpGroupID) VALUES(1000)
INSERT INTO Emp(EmpGroupID) VALUES(1000)
INSERT INTO Emp(EmpGroupID) VALUES(1000)
INSERT INTO Emp(EmpGroupID) VALUES(2000)
INSERT INTO Emp(EmpGroupID) VALUES(2000)
INSERT INTO Emp(EmpGroupID) VALUES(2000)
INSERT INTO Emp(EmpGroupID) VALUES(3000)
GO
SELECT * FROM Emp
ORDER BY EmpGroupID,EmpID

What I need is for each group to have a counter variable, incrementing by 1, such that all the rows for Group 1000 have counter=1, groupid=2000 has counter=2, groupid=3000 has counter=3.

SELECT ?,EmpID,EmpGroupID 
FROM Emp
ORDER BY EmpGroupID,EmpID
-- The result I'm looking for is:
1,10,1000
1,11,1000
1,12,1000
2,13,2000
2,14,2000
2,15,2000
3,16,3000

Answer 1

You’re describing a dense ranking of groups:

SELECT
  DENSE_RANK() OVER (ORDER BY EmpGroupID) as Counter,
  EmpID,
  EmpGroupID
FROM Emp
ORDER BY EmpGroupID,EmpID

And here’s some reference material: http://msdn.microsoft.com/en-us/library/ms189798.aspx