Get all employee who directly or indirectly reports to an employee, with hierarchy level no

问题

I have a Employee table like

emp_id bigint,
reports_to bigint,
emp_name varchar(20),
Constraint [PK_Emp] Primary key (emp_id),
Constraint [FK_Emp] Foreign key (reports_to) references [MSS].[dbo].[Emp]([emp_id])

emp_id         reports_to        emp_name
------         ------       --------------
1              null         Sumanta
2              1            Arpita
3              null         Pradip
4              1            Sujon
5              2            Arpan
6              5            Jayanti

I want to get all the employees that directly or indirectly reports to Sumanta or emp_id(1), and with hierarchy level, like this:

emp_id         hierarchy_level         emp_name
------         ---------------        ----------
2                    1                  Arpita
4                    1                  Sujon
5                    2                  Arpan
6                    3                 Jayanti

I am new to SQL and just couldn't find what to use or how to get those results. Is it worth a stored procedure with table valued variable, or just a Tsql select query will be enough. Any help is most welcome.

All I have done is-

Select Ep.emp_id,ep.emp_eame 
From Emp as E 
Inner Join Emp as Ep on Ep.reports_to=E.Emp_id 
Where E.reports_to=1 or E.emp_id=1;

but this is accurate upto 2 level and I cant even generate the hierarchy_level no. Any suggestion, idea............ will be most helpfull.........

回答1:

You could use a recursive CTE:

; with  CTE as 
        (
        select  emp_id
        ,       reports_to
        ,       emp_name
        ,       1 as level
        from    Emp
        where   emp_name = 'Sumanta'
        union all
        select  child.emp_id
        ,       child.reports_to
        ,       child.emp_name
        ,       level + 1
        from    Emp child
        join    CTE parent
        on      child.reports_to = parent.emp_id
        )
select  *
from    CTE

Example at SQL Fiddle.

来源：https://stackoverflow.com/questions/16232426/get-all-employee-who-directly-or-indirectly-reports-to-an-employee-with-hierarc

标签

sql

sql-server

foreign-keys

iteration

primary-key