Sql查询树状结构下级子节点的数量

--查询Id为1的所有子节点层数的数量
;with cte as
(
select id,parentId,0 as Leave from _TestLeave where id = 1　　--要查询的节点
union all
select a.id,a.parentId,b.Leave + 1 as Leave from _TestLeave a join cte b on a.parentId = b.id 
and b.Leave < 6　　--层数
)
select leave,count(*) from cte where leave > 0 group by Leave