【Sql Server】SQL SERVER 遞歸查詢

　　SQL SERVER 2005之前的版本只能用函數方法實現，SQL SERVER 2005之后新增了CTE功能，可以利用CTE實現遞歸查詢；

　　CTE：公用表達式Common Table Expression 是SQL SERVER 2005版本之后引入的一個特性；

#填充測試數據

1、sql

Create table GroupInfo([Id] int,[GroupName] nvarchar(50),[ParentGroupId] int)

Insert GroupInfo

select 0,'某某大學',null union all

select 1,'外語學院',0 union all
select 2,'英語專業',1 union all
select 3,'日語專業',1 union all
select 4,'英語專業一班',2 union all
select 5,'英語專業二班',2 union all
select 6,'日語專業一班',3 union all
select 7,'日語專業二班',3 union all

select 8, '法學院',0 union all
select 9, '刑法學專業',8 union all
select 10,'經濟法學專業',8 union all
select 11,'刑法學專業一班',9 union all
select 12,'刑法學專業二班',9 union all
select 13,'經濟法學專業一班',10 union all
select 14,'經濟法學專業二班',10 

2、效果圖

 

#遞歸實現Demo

1、根據指定的節點向上獲取所有父節點,向下獲取所有子節點

--根據指定的節點向下獲取所有子節點
with
CTE
as
(
    select * from GroupInfo where Id=1
    union all
    select G.* from CTE inner join GroupInfo as G
    on CTE.Id=G.ParentGroupId
)
select * from CTE order by Id

 

--根據指定的節點向上獲取所有父節點
with
CTE
as
(
    select * from GroupInfo where Id=14
    union all
    select G.* from CTE inner join GroupInfo as G
    on CTE.ParentGroupId=G.Id
)
select * from CTE order by Id

2、構造遞歸路徑

--構造遞歸路徑
with
CTE
as
(
    select Id,GroupName,ParentGroupId,GroupPath=CAST( GroupName as nvarchar(max)) from GroupInfo where Id=1
    union all
    select G.*,CAST(CTE.GroupPath+'//'+G.GroupName as nvarchar(max)) as GroupPath from CTE 
    inner join GroupInfo as G
    on CTE.Id=G.ParentGroupId
)
select * from CTE

 3、分組遞歸，將同一條分支上節點放到一起

--通過id字段的字符串的拼接，形成sort字段，再通過sort排序，來實現同一分支上的節點放到一起
WITH    
CTE
AS 
( 
    SELECT * ,CAST(RIGHT('000' + CAST([Id] AS VARCHAR), 3) AS VARCHAR(MAX)) AS sort FROM GroupInfo
    WHERE ParentGroupId = 0
    UNION ALL
    SELECT   GroupInfo.* ,CAST(sort + RIGHT('000' + CAST(GroupInfo.[Id] AS VARCHAR),3) AS VARCHAR(MAX)) AS sort
    FROM CTE
    INNER JOIN GroupInfo ON CTE.Id = GroupInfo.ParentGroupId
)
SELECT * FROM CTE ORDER BY sort 

 

4、遞歸層級查詢（查詢出節點所屬的層級）

--查詢節點層級
WITH CTE AS (
    SELECT *,1 AS [Level] FROM GroupInfo WHERE ParentGroupId=0
    UNION ALL
    SELECT G.*,CTE.Level+1 FROM GroupInfo as G 
    JOIN CTE ON CTE.Id =G.ParentGroupId
)
SELECT * FROM CTE