【100分，确实有些疑难】关于按照某个字段部分内容来进行Group By的有关问题

------------------------------ Author  :SQL77(只为思齐老)-- Date    :2010-03-09 15:17:54-- Version:--      Microsoft SQL Server  2000 - 8.00.194 (Intel X86) --    Aug  6 2000 00:57:48 --    Copyright (c) 1988-2000 Microsoft Corporation--    Desktop Engine on Windows NT 5.1 (Build 2600: Service Pack 3)--------------------------------> 测试数据：#TBif object_id('tempdb.dbo.#TB') is not null drop table #TBgo create table #TB([Mail_From] varchar(6),[Mail_To] varchar(40))insert #TBselect 'liming',[email protected];[email protected];[email protected]' union allselect 'liming',[email protected]' union allselect 'liming',[email protected]' union allselect 'liming',[email protected];[email protected]' union allselect 'liming',[email protected]' union allselect 'liming',[email protected];[email protected]'--------------开始查询--------------------------SELECT  Mail_From, Mail_TO,COUNT(1) C FROM (select Mail_From,SUBSTRING( Mail_To,NUMBER,CHARINDEX(';',Mail_To+';',NUMBER)-NUMBER)Mail_ToFROM  #TB,MASTER..SPT_VALUES WHERE TYPE='P' AND SUBSTRING(';'+Mail_To,NUMBER,1)=';')T GROUP BY Mail_From, Mail_TO ORDER BY 3 DESC----------------结果----------------------------（所影响的行数为 6 行）Mail_From Mail_TO                                  C           --------- ---------------------------------------- ----------- liming    [email protected]                         4liming    [email protected]                              3liming    [email protected]                              2liming    [email protected]                         1（所影响的行数为 4 行）/* */
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--> 测试数据：[tb]if object_id('[tb]') is not null drop table [tb]create table [tb]([Mail_From] varchar(6),[Mail_To] varchar(40))goinsert [tb]select 'liming',[email protected];[email protected];[email protected]' union allselect 'liming',[email protected]' union allselect 'liming',[email protected]' union allselect 'liming',[email protected];[email protected]' union allselect 'liming',[email protected]' union allselect 'liming',[email protected];[email protected]'select Mail_To=substring(t.Mail_To,r.number,charindex(';',t.Mail_To+';',r.number)-r.number),count(1) as Numfrom tb t,master..spt_values rwhere r.number<=len(t.Mail_To) and r.type='p' and substring(';'+t.Mail_To,r.number,1)=';'group by substring(t.Mail_To,r.number,charindex(';',t.Mail_To+';',r.number)-r.number)Mail_To                                  Num         ---------------------------------------- ----------- [email protected]                              3[email protected]                         1[email protected]                              2[email protected]                         4（所影响的行数为 4 行）
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--参考拆分表:--> --> (Roy)生成測試數據 if not object_id('Tab') is null    drop table TabGoCreate table Tab([Col1] int,[COl2] nvarchar(5))Insert Tabselect 1,N'a,b,c' union allselect 2,N'd,e' union allselect 3,N'f'Go--SQL2000用辅助表:if object_id('Tempdb..#Num') is not null    drop table #Numgoselect top 100 ID=Identity(int,1,1) into #Num from syscolumns a,syscolumns bSelect     a.Col1,COl2=substring(a.Col2,b.ID,charindex(',',a.Col2+',',b.ID)-b.ID) from     Tab a,#Num bwhere    charindex(',',','+a.Col2,b.ID)=b.ID --也可用 substring(','+a.COl2,b.ID,1)=','--2000不使用辅助表Select    a.Col1,COl2=substring(a.Col2,b.number,charindex(',',a.Col2+',',b.number)-b.number) from     Tab a join master..spt_values  b     ON B.type='p' AND B.number BETWEEN 1 AND LEN(A.col2)where     substring(','+a.COl2,b.number,1)=','SQL2005用Xml:select     a.COl1,b.Col2from     (select Col1,COl2=convert(xml,'<root><v>'+replace(COl2,',','</v><v>')+'</v></root>') from Tab)aouter apply    (select Col2=C.v.value('.','nvarchar(100)') from a.COl2.nodes('/root/v')C(v))bSQL05用CTE:;with roy as (select Col1,COl2=cast(left(Col2,charindex(',',Col2+',')-1) as nvarchar(100)),Split=cast(stuff(COl2+',',1,charindex(',',Col2+','),'') as nvarchar(100)) from Tabunion allselect Col1,COl2=cast(left(Split,charindex(',',Split)-1) as nvarchar(100)),Split= cast(stuff(Split,1,charindex(',',Split),'') as nvarchar(100)) from Roy where split>'')select COl1,COl2 from roy order by COl1 option (MAXRECURSION 0)生成结果:/*Col1        COl2----------- -----1           a1           b1           c2           d2           e3           f*/