以下模拟一下CTE出错

/*测试环境

Microsoft SQL Server 2008 R2 (RTM) - 10.50.1600.1 (X64)   Apr  2 2010 15:48:46   Copyright (c) Microsoft Corporation  Developer Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1)

*/

生成表Tab数据：

--> --> (Roy)生成測試數據

if not object_id('Tab') is null

    drop table Tab

Go

Create table Tab([Col1] int,[COl2] nvarchar(5))

Insert Tab

select 1,N'a,b,c' union all

select 2,N'd,e' union all

select 3,N'f'

Go

方法1:用CTE引发函数出错

if object_id('Tempdb..#Tab') is not null

    drop table #Tab

select top 100 ID=Identity(int,1,1) into #Tab from syscolumns a,syscolumns b

declare @Str varchar(10)='a'

;with Cte

as

(

Select

    a.Col1,COl2=substring(a.Col2,b.ID,charindex(',',a.Col2+',',b.ID)-b.ID)

from

    Tab a,#Tab b

where

    charindex(',',','+a.Col2,b.ID)=b.ID --也可用 substring(','+a.COl2,b.ID,1)=','

)

select Col1 from Cte where @str=COl2

/*

消息 537，级别 16，状态 3，第 8 行

传递给 LEFT 或 SUBSTRING 函数的长度参数无效。

*/

方法2：直接用语句时不会报错：

if object_id('Tempdb..#Tab') is not null

    drop table #Tab

select top 100 ID=Identity(int,1,1) into #Tab from syscolumns a,syscolumns b

declare @Str varchar(10)='a'

Select

    a.Col1

from

    Tab a,#Tab b

where

    charindex(',',','+a.Col2,b.ID)=b.ID --也可用 substring(','+a.COl2,b.ID,1)=','

and substring(a.Col2,b.ID,charindex(',',a.Col2+',',b.ID)-b.ID) =@Str

/*

Col1

1

*/

方法3:把Where条件换一下顺序也出错

if object_id('Tempdb..#Tab') is not null

    drop table #Tab

select top 100 ID=Identity(int,1,1) into #Tab from syscolumns a,syscolumns b

go

declare @Str varchar(10)='a'

Select

    a.Col1

from

    Tab a,#Tab b

where

    substring(a.Col2,b.ID,charindex(',',a.Col2+',',b.ID)-b.ID) =@Str and charindex(',',','+a.Col2,b.ID)=b.ID --也可用 substring(','+a.COl2,b.ID,1)=','

查原因从执行计划来找

if object_id('Tempdb..#Tab') is not null

    drop table #Tab

select top 100 ID=Identity(int,1,1) into #Tab from syscolumns a,syscolumns b

go

SET SHOWPLAN_ALL ON;

go

--a.查看方法1执行计划

declare @Str varchar(10)='a'

;with Cte

as

(

Select

    a.Col1,COl2=substring(a.Col2,b.ID,charindex(',',a.Col2+',',b.ID)-b.ID)

from

    Tab a,#Tab b

where

    charindex(',',','+a.Col2,b.ID)=b.ID --也可用 substring(','+a.COl2,b.ID,1)=','

)

select Col1 from Cte where @str=COl2

go

--b.查看方法2执行计划

declare @Str varchar(10)='a'

Select

    a.Col1

from

    Tab a,#Tab b

where

    charindex(',',','+a.Col2,b.ID)=b.ID --也可用 substring(','+a.COl2,b.ID,1)=','

and substring(a.Col2,b.ID,charindex(',',a.Col2+',',b.ID)-b.ID) =@Str

go

SET SHOWPLAN_ALL off

go