CREATE PROCEDURE [p_try] AS
declare @sql varchar(8000)
set @sql=''
select @sql=@sql+ltrim(str(id) ) +',' from tree
select a=@sql
GOuse tempdb
go
exec p_try
declare @sql varchar(8000)
set @sql=''
select @sql=@sql+ltrim(str(id) ) +',' from tree
select a=@sql
GOuse tempdb
go
exec p_try
set @sql=''不初始化的话,@sql的值为null,而null与任何值的计算结果都还是null,所以就没结果了.
大师,带我奔小康吧!