检测数据表是否存在指定列

检测数据表是否存在指定列，如果不存在，则新增列

if  (NOT   exists (  select   *   from  dbo.syscolumns  where  name  =   ' sum '   and  id  in  
( select  id  from  dbo.sysobjects  where  id  =   object_id (N ' [dbo].[T_TestTable] ' )  and   OBJECTPROPERTY (id, N ' IsUserTable ' )  =   1 ))
)