Question

有两个表，一个包含分层员工数据，

Id，Name，ManagerId

1，Boss，NULL

2，经理A，1

3，经理B，1

4，LeadC，2

5，EngineerD，4

...

另一张表包含谁是每个部门的负责人

Id，Department

2，发展

3，销售

4，ProjectX

现在我想基于第一个表创建一个View，但是还有一个Department列，由最近的祖先确定，该祖先在表2中有条目。是否可以使用单个SQL语句？

Id，Name，ManagerId，Department

1，Boss，NULL，NULL

2，经理A，1，发展

3，经理B，1，销售

4，LeadC，2，ProjectX

5，EngineerD，4，ProjectX

Answer 1

递归公用表表达式将遍历层次结构

with ed as (
    select
        employee.id, employee.managerid, department.department
    from employee left join department on  employee.Id = department.Id 
    where department is not null
    union all 
    select
        employee.id, employee.managerid, department.department
    from employee 
    inner join ed on employee.managerid = ed.id
    inner join department on  ed.Id = department.Id 
)
select * From ed

回答改编自http://blog.sqlauthority.com/2012/04/24/sql-server-introduction-to-hierarchical-query-using-a-recursive-cte-a-primer/

Answer 2

select employeedata.id,name,managerId,
case when DepartmentName 
is null then (select departmentName from department where id =managerID )
else DepartmentName
end as dep2
from employeeData
left join 
department on employeeData.id=department.id

see you sql demo

Answer 3

这样做：

SELECT e.*,
CASE h1.Department IS NULL h2.Department ELSE h1.Department END AS Department
from employee e
LEFT JOIN heads h1 ON e.id = h1.id
LEFT JOIN heads h2 ON e.ManagerId = h2.id

用于查找每行的祖先的SQL语句

3 个答案: