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连接两个表,其中在另一个表上选择最高值

greatest-n-per-group sql-server-2008 sql

0

Ryan · 技术社区 · 9 年前

WITH CTE AS 
(
    SELECT DocNum, Status 
    FROM TableB 
    WHERE Id = (SELECT MAX(Id) FROM  TableB)
)
SELECT  TableA.DocNum, DocTitle, cte.Status
FROM TableA
INNER JOIN cte 
ON TableA.DocNum = cte.DocNum

示例如下:

Table A
    Id DocNum  DocTitle
    1  ST-0001 SomeTitle
    2  ST-0002 SomeTitle
    3  ST-0003 SomeTitle
    4  ST-0004 SomeTitle
    5  ST-0005 SomeTitle

Table B
    Id DocNum Status
    1  ST-0001 Incomplete
    2  ST-0001 Complete
    3  ST-0002 Complete
    4  ST-0003 Incomplete
    5  ST-0004 Incomplete
    6  ST-0004 Complete 
    7  ST-0005 Incomplete   

Result
    DocNum DocTitle Status
    ST-0001 SomeTitle Complete  
    ST-0002 SomeTitle Complete  
    ST-0003 SomeTitle Incomplete  
    ST-0004 SomeTitle Complete  
    ST-0005 SomeTitle Incomplete

1 回复 | 直到 9 年前

1

0

Zohar Peled 9 年前

您可以使用具有Row_number的CTE从tableB中仅获取每个docNum具有最大id的行,然后加入该CTE。

首先,创建并填充样本表( 请请在您未来的问题中为我们保留此步骤):

DECLARE @A As Table
(
    Id int,
    DocNum char(7),
    DocTitle varchar(20)
);

DECLARE @B As Table
(
    Id int,
    DocNum char(7),
    [Status] varchar(20)
);

INSERT INTO @A VALUES
(1, 'ST-0001', 'SomeTitle'),
(2, 'ST-0002', 'SomeTitle'),
(3, 'ST-0003', 'SomeTitle'),
(4, 'ST-0004', 'SomeTitle'),
(5, 'ST-0005', 'SomeTitle');

INSERT INTO @B VALUES
(1, 'ST-0001', 'Incomplete'),
(2, 'ST-0001', 'Complete'),
(3, 'ST-0002', 'Complete'),
(4, 'ST-0003', 'Incomplete'),
(5, 'ST-0004', 'Incomplete'),
(6, 'ST-0004', 'Complete'),
(7, 'ST-0005', 'Incomplete');

;WITH CTE AS
(
    SELECT  Id, 
            DocNum, 
            [Status],
            ROW_NUMBER() OVER(PARTITION BY DocNum ORDER BY Id DESC) As Rn
    FROM @B
)

SELECT A.DocNum, A.DocTitle, CTE.[Status]
FROM @A A 
INNER JOIN CTE ON A.DocNum = CTE.DocNum
WHERE CTE.rn = 1

结果:

DocNum      DocTitle    Status
ST-0001     SomeTitle   Complete  
ST-0002     SomeTitle   Complete  
ST-0003     SomeTitle   Incomplete  
ST-0004     SomeTitle   Complete  
ST-0005     SomeTitle   Incomplete

You can see a live demo on rextester.