SQL按组选择计数器

Question

这是我编写的用于创建场景的代码：

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

我需要的是每个组都有一个计数器变量，递增1，这样，组1000的所有行的计数器都为counter = 1，groupid = 2000的计数器为counter = 2，groupid = 3000的计数器为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

您正在描述密集的组排名：

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

以下是一些参考资料：http : //msdn.microsoft.com/zh-cn/library/ms189798.aspx