SQL Server 公用表表达式(CTE)实现递归的方法

create table Role_CTE
(
 Id  int    not null,
 Name nvarchar(32) not null,
 ParentId int  not null 
)
insert into Role_CTE(Id,Name,ParentId)
select '1','超级管理员','0' union 
select '2','管理员A','1' union 
select '3','管理员B','2' union 
select '4','会员AA','2' union 
select '5','会员AB','2' union 
select '6','会员BA','3' union 
select '7','会员BB','3' union 
select '8','用户AAA','4' union 
select '9','用户BBA','7' 
-- 创建一个复合聚集索引
create clustered index Clu_Role_CTE_Index
on Role_CTE(Id,ParentId)
with
(
 pad_index=on,
 fillfactor=50,
 drop_existing=off,
 statistics_norecompute=on
)
select * from Role_CTE

declare @level int
declare @node int
declare @ResTab table
(
 node int not null,
 lv  int not null 
)
set @level=0  -- 表示初始的等级
set @node=3   --表示初始的节点ID,即从指定的哪个节点开始查找
insert into @ResTab    -- 为表变量插入初始的数据
select Id,@level 
from Role_CTE 
where Id=@node
while(@@ROWCOUNT>0)
begin
 set @level=@level+1
 insert into @ResTab
 select b.Id,@level 
 from @ResTab a 
 join Role_CTE b on a.node=b.ParentId and lv=@level-1 -- join 等于 inner join（内连接）和自连接
end
select a.node,b.Name,a.lv 
from @ResTab a 
left join Role_CTE b on a.node=b.Id

declare @level int
declare @node int
declare @num int
declare @ResTab table
(
 node int not null,
 lv  int not null 
)
set @level=0  -- 表示初始的等级
set @node=3   --表示初始的节点ID,即从指定的哪个节点开始查找
set @num=1  -- 指定递归层级，即循环的次数
insert into @ResTab    -- 为表变量插入初始的数据
select Id,@level 
from Role_CTE 
where Id=@node
while(@@ROWCOUNT>0 and @level<@num)
begin
 set @level=@level+1
 insert into @ResTab
 select b.Id,@level 
 from @ResTab a 
 join Role_CTE b on a.node=b.ParentId and lv=@level-1 -- join 等于 inner join（内连接）和自连接
end
select a.node,b.Name,a.lv 
from @ResTab a 
left join Role_CTE b on a.node=b.Id

declare @node int 
set @node=3;
with temp_cte
as
(
 select Id,Name,0 lv  -- 查询出“根节点”，即指定的起始节点
 from Role_CTE 
 where Id=@node 
 union all
 select b.Id,b.Name,a.lv+1 
 from temp_cte a 
 join Role_CTE b on a.Id=b.ParentId
)
select * from temp_cte

declare @node int 
declare @num int
set @node=3;
set @num=1;
with temp_cte
as
(
 select Id,Name,0 lv  -- 查询出“根节点”，即指定的起始节点
 from Role_CTE 
 where Id=@node 
 union all
 select b.Id,b.Name,a.lv+1 
 from temp_cte a 
 join Role_CTE b on a.Id=b.ParentId
     and a.lv<@num  --控制递归层数
)
select * from temp_cte

declare @level int
declare @node int
declare @num int
declare @ResTab table
(
 node int not null,
 lv  int not null 
)
set @level=0 -- 表示初始的等级
set @node=8   --表示初始的节点ID,即从指定的哪个节点开始查找
set @num=2  -- 指定递归层级，即循环的次数
while(@level<=@num and @node is not null) -- 如果为空就表示没有查到父级了
begin
 insert into @ResTab
 select @node,@level
 set @level=@level+1
 select @node=ParentId 
 from Role_CTE 
 where Id=@node
end
select a.node,b.Name,a.lv 
from @ResTab a 
left join Role_CTE b on a.node=b.Id

declare @node int 
declare @num int
set @node=8;
set @num=2;
with temp_cte
as
(
 select Id,Name,ParentId,0 lv  -- 查询出“根节点”，即指定的起始节点
 from Role_CTE 
 where Id=@node 
 union all
 select b.Id,b.Name,b.ParentId,a.lv+1 
 from temp_cte a 
 join Role_CTE b on a.ParentId=b.Id
     and a.lv < @num  --控制递归层数
)
select * from temp_cte