SQL SERVER CTE递归算法

可以用于TREEW上面

创建一个表：

create table test
(
    indexid int,
    textvalue nvarchar(20),
    parentid int
)

插入一些测试数据：

insert into test values(1,'10',0)
insert into test values(2,'20',0)
insert into test values(3,'30',0)
insert into test values(4,'40',0)
insert into test values(5,'50',0)
insert into test values(10,'100',1)
insert into test values(11,'110',1)
insert into test values(12,'120',1)
insert into test values(100,'1000',10)
insert into test values(110,'1100',10)
insert into test values(120,'1200',10)
insert into test values(130,'1300',10)
insert into test values(1000,'10000',100)
insert into test values(1100,'11000',100)
insert into test values(1200,'12000',100)
insert into test values(1300,'13000',100)
insert into test values(20,'200',2)
insert into test values(21,'210',2)
insert into test values(22,'220',2)
insert into test values(200,'2000',20)
insert into test values(210,'2100',20)

执行测试Sql语句：

GO
WITH DirectReports (indexid, textvalue,parentid,Level)
AS
(
    SELECT e.indexid, e.textvalue,e.parentid, 0 AS Level
    FROM test AS e where indexid=1 --起始节点
    UNION ALL --用于合并两个或多个 SELECT 语句的结果集。
    SELECT e.indexid, e.textvalue,e.parentid,Level + 1
    FROM test AS e
    INNER JOIN --在表中存在至少一个匹配时，INNER JOIN 关键字返回行。

   DirectReports AS d
        ON e.parentid = d.indexid
)
SELECT indexid, textvalue,parentid,Level FROM DirectReports
GO

执行结果如图：