sqlserver 中ntext字段的批量替换（updatetext的用法）

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