t-sql分组查询

Question

基于下表

Name
---------
A
A
A
B
B
C
C
C

我想在此表中添加另一个名为"OnGoing"的列,并且值应该替换为每组名称.只有两个值'X'和'Y'.所以表格看起来像

Name     OnGoing
----------------
A        X
A        X
A        X 
B        Y
B        Y
C        X
C        X 
C        X

如何编写这样的查询,可以替换每组名称的值.

Answer 1

怎么样的

DECLARE @Table TABLE(
        Name VARCHAR(10)
)

INSERT INTO @Table SELECT 'A'
INSERT INTO @Table SELECT 'A' 
INSERT INTO @Table SELECT 'A' 
INSERT INTO @Table SELECT 'B' 
INSERT INTO @Table SELECT 'B' 
INSERT INTO @Table SELECT 'C' 
INSERT INTO @Table SELECT 'C' 
INSERT INTO @Table SELECT 'C' 

SELECT  *,
        CASE 
            WHEN RowNum % 2 = 0 
                THEN 'Y'
            ELSE 'X'
        END
FROM    @Table t INNER JOIN
        (
            SELECT  Name,
                    ROW_NUMBER() OVER (ORDER BY Name) RowNum
            FROM    @Table
            GROUP BY Name
        ) sub ON t.Name = sub.Name