sqlserver中ntext字段的批量替换（updatetext的用法）

在Sql Server 中，ntext/text/image 字段不允许应用replace函数替换内容

CREATE procedure [dbo].[Proc_UpdateNTextField] 
@TargetTable nvarchar(1000), --目标表名 
@TargetField nvarchar(1000), --目标字段名 
@PKField nvarchar(1000), --该表主键字段名 
@otxt nvarchar(1000),         --需要替换的字符串 
@ntxt nvarchar(1000)         --替换后的字符串 
as 
begin 
declare @SqlStr nvarchar(4000) 
set @SqlStr = ' declare @txtlen int ' 
set @SqlStr = @SqlStr + ' set @txtlen = len(''' + @otxt + ''') ' 
set @SqlStr = @SqlStr + ' declare @pos int ' 
set @SqlStr = @SqlStr + ' set @pos = 0 ' 
set @SqlStr = @SqlStr + 'declare curs cursor local fast_forward for select ' 
set @SqlStr = @SqlStr + @PKField + ' , textptr(' + @TargetField +') from ' + @TargetTable +' where ' + @TargetField + ' like ''%' + @otxt +'%''' 
set @SqlStr = @SqlStr + ' declare @ptr binary(16) ' 
set @SqlStr = @SqlStr + ' declare @id char(32) ' 
set @SqlStr = @SqlStr + ' open curs ' 
set @SqlStr = @SqlStr + ' fetch next from curs into @id, @ptr ' 
set @SqlStr = @SqlStr + ' while @@fetch_status = 0 ' 
set @SqlStr = @SqlStr + ' begin ' 
set @SqlStr = @SqlStr + ' select @pos= patindex(''%' + @otxt + '%'',ProductDesc) from ProductTemp where ProductID=@id ' 
set @SqlStr = @SqlStr + ' while @pos>0 ' 
set @SqlStr = @SqlStr + ' begin ' 

set @SqlStr = @SqlStr + ' set @pos=@pos-1 ' 
set @SqlStr = @SqlStr + ' updatetext ' + @TargetTable + '.' +@TargetField + ' @ptr @pos @txtlen ''' + @ntxt + ''' ' 
set @SqlStr = @SqlStr + ' select @pos= patindex(''%' + @otxt + '%'',ProductDesc) from ProductTemp where ProductID=@id ' 
set @SqlStr = @SqlStr + ' end ' 
set @SqlStr = @SqlStr + ' fetch next from curs into @id, @ptr ' 
set @SqlStr = @SqlStr + ' end ' 
set @SqlStr = @SqlStr + ' close curs ' 
set @SqlStr = @SqlStr + ' deallocate curs ' 
EXECUTE sp_executesql @SqlStr 
end