SQL SERVER2005---CTE表达式

今天做项目刚好需要一个获得每个节点的levelno,就想起了sql2005的CTE表达式,试用了一下,效果不错.

 我的理解CTE是可以复用的虚拟表,它可以实现自递归.

参考文章:Sql Server2005 Transact-SQL 新兵器学习总结之-公用表表达式(CTE)

WITH    BaseFundsProject_CTE ( Id, Code, ParentId, [Name], LevelNo, YearNo, ShowOrder, [Description], IsActiveFlag )
      AS ( SELECT   Id ,
                    Code ,
                    ParentId ,
                    [Name] ,
                    1 AS LevelNo ,
                    YearNo ,
                    ShowOrder ,
                    [Description] ,
                    IsActiveFlag
           FROM     BaseFundsProject
           WHERE    ISNULL(ParentId, '') = ''
                    AND YearNo = @YearNo
           UNION ALL
           SELECT   c.Id ,
                    c.Code ,
                    c.ParentId ,
                    c.[Name] ,
                    LevelNo + 1 ,
                    C.YearNo ,
                    C.ShowOrder ,
                    C.[Description] ,
                    C.IsActiveFlag
           FROM     BaseFundsProject c
                    INNER JOIN BaseFundsProject_CTE ct ON c.ParentId = ct.Code
                                                      AND C.YearNo = @YearNo
         )
SELECT  Id ,
        Code ,
        ParentId ,
        [Name] ,
        LevelNo ,
        YearNo ,
        ShowOrder ,
        [Description] ,
        IsActiveFlag
FROM    BaseFundsProject_CTE
ORDER BY Code