SQL SERVER CTE递归查询

SQL SERVER CTE递归查询

正文

　　SQL SERVER 2005之前的版本只能用函数方法实现，SQL SERVER 2005之后新增了CTE(Common Table Expression)功能，可以利用CTE实现递归查询；

 

一、建表

1、sql

 

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

Insert test_GroupInfo

select 0,'某某大学',null union all

select 1,'外语学院',0 union all
select 2,'英语专业',1 union all
select 3,'日语专业',1 union all
select 4,'英语专业一班',2 union all
select 5,'英语专业二班',2 union all
select 6,'日语专业一班',3 union all
select 7,'日语专业二班',3 union all

select 8, '法学院',0 union all
select 9, '刑法学专业',8 union all
select 10,'经济法学专业',8 union all
select 11,'刑法学专业一班',9 union all
select 12,'刑法学专业二班',9 union all
select 13,'经济法学专业一班',10 union all
select 14,'经济法学专业二班',10

2、效果图

 

 

二、递归实现Demo

1、根据指定的节点向上获取所有父节点,向下获取所有子节点

--根据指定的节点向下获取所有子节点
with
CTE
as
(
    select * from test_GroupInfo where Id=1
    union all
    select G.* from CTE inner join test_GroupInfo as G
    on CTE.Id=G.ParentGroupId
)
select * from CTE order by Id

--根据指定的节点向上获取所有父节点
with
CTE
as
(
    select * from test_GroupInfo where Id=14
    union all
    select G.* from CTE inner join test_GroupInfo as G
    on CTE.ParentGroupId=G.Id
)
select * from CTE order by Id

 2、构造递归路径

--构造递归路径
with
CTE
as
(
    select Id,GroupName,ParentGroupId,GroupPath=CAST( GroupName as nvarchar(max)) from test_GroupInfo where Id=1
    union all
    select G.*,CAST(CTE.GroupPath+'//'+G.GroupName as nvarchar(max)) as GroupPath from CTE
    inner join test_GroupInfo as G
    on CTE.Id=G.ParentGroupId
)
select * from CTE

 3、分组递归，将同一条分支上节点放到一起

--通过id字段的字符串的拼接，形成sort字段，再通过sort排序，来实现同一分支上的节点放到一起
WITH
CTE
AS
(
    SELECT * ,CAST(RIGHT('000' + CAST([Id] AS VARCHAR), 3) AS VARCHAR(MAX)) AS sort FROM test_GroupInfo
    WHERE ParentGroupId = 0
    UNION ALL
    SELECT   test_GroupInfo.* ,CAST(sort + RIGHT('000' + CAST(test_GroupInfo.[Id] AS VARCHAR),3) AS VARCHAR(MAX)) AS sort
    FROM CTE
    INNER JOIN test_GroupInfo ON CTE.Id = test_GroupInfo.ParentGroupId
)
SELECT * FROM CTE ORDER BY sort


select id,CAST(RIGHT('000' + CAST([Id] AS VARCHAR), 3) AS VARCHAR(MAX)) from test_GroupInfo

4、递归层级查询（查询出节点所属的层级）

--查询节点层级
WITH CTE AS (
    SELECT *,1 AS [Level] FROM test_GroupInfo WHERE ParentGroupId=0
    UNION ALL
    SELECT G.*,CTE.Level+1 FROM test_GroupInfo as G
    JOIN CTE ON CTE.Id =G.ParentGroupId
)
SELECT * FROM CTE

转载自：https://www.cnblogs.com/linyuansun/p/14283550.html