SQL查询每行中最大值的技巧

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--  Author : htl258(Tony)
--  Date   : 2010-04-23 08:08:36
--  Version:Microsoft SQL Server 2008 (RTM) - 10.0.1600.22 (Intel X86)
--          Jul  9 2008 14:43:34
--          Copyright (c) 1988-2008 Microsoft Corporation
--          Developer Edition on Windows NT 5.1 <X86> (Build 2600: Service Pack 3)
--  Blog   : http://blog.csdn.net/htl258
--  Subject: SQL查询每行中最大值的技巧
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--> 生成测试数据表:tb
 
IF NOT OBJECT_ID('[tb]') IS NULL
    DROP TABLE [tb]
GO
CREATE TABLE [tb](
a SMALLINT,
b SMALLINT,
c SMALLINT,
d SMALLINT,
e SMALLINT,
f SMALLINT,
g SMALLINT
)
INSERT [tb]
SELECT 1,2,3,4,5,2,3 UNION ALL
SELECT 4,5,6,7,7,2,0 UNION ALL
SELECT 4,9,6,7,7,9,6
GO
--SELECT * from [tb]
 
-->SQL查询如下:
 
SELECT *,
    (SELECT MAX(a)
     from(
       SELECT a UNION ALL
       SELECT b UNION ALL
       SELECT c UNION ALL
       SELECT d UNION ALL
       SELECT e UNION ALL
       SELECT f UNION ALL
       SELECT g
       ) AS t  
    ) AS maxvalue
from tb
 
 
/*
a      b      c      d      e      f      g      maxvalue
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