sql 递归

sql server: 递归求级别level

with directreports as
(
--定位点成员定义
select managerid,employeeid,0 as level
from employees
where managerid is null 
union all
--递归成员定义
select e.managerid,e.employeeid,d.level+1
from employees as e
inner join directreports as d
on e.managerid=d.employeeid
)
--执行cte语句
select * from directreports
option  (maxrecursion 4);

CREATE TABLE [dbo].[employees](
    [employeeid] [int] NOT NULL,
    [managerid] [int] NULL,
    [employeename] [char](10) NOT NULL,
    [salary] [money] NOT NULL
) ON [PRIMARY]

employeeid    managerid    employeename    salary
1    NULL    a1            10000.00
2    1    b1            9000.00
3    1    b2            9000.00
4    2    c1            9000.00
5    2    c2            8000.00
6    3    c3            8000.00