问题描述
需要传递员工ID并获得在SQL中传递员工ID的经理下工作的员工总数。
Out应该是这样的： -
EmplD NoofEmployees
1234 10
2562 25
其中10& 25实际上是在EmplD 1234和2562的经理下工作的员工总数。
我尝试了什么：
我尝试过CTE和自我加入，但我需要一个性能更好的解决方案。
Need to Pass employee Id and get total number of employees working under the manager whose employee id is passed in SQL.
Out should be like this : -
EmplD NoofEmployees
1234 10
2562 25
Where 10 & 25 is actually the total number of employees working under the manager of EmplD 1234 and 2562 resp.
What I have tried:
I tried CTE and Self Join but i need a solution with better performance.
推荐答案
Employees: ID Name ManagerID然后是一个简单的GROUP BY会这样做：
Then a simple GROUP BY will do it:
SELECT ManagerID, COUNT(ID) FROM Employees GROUP BY ManagerID如果不是在我们开始回答之前，我们需要更多信息。
表格是这样的：
在GROUP中使用JOIN：
If it isn't, we'd need a load more info before we could begin to answer.
"The Table is something like this :"
Use a JOIN with the GROUP by:
SELECT e.ID, e.Name, m.MngCount FROM EMPLOYEE e
JOIN (SELECT ManagerID, COUNT(ID) as MngCount FROM Employees GROUP BY ManagerID) m
ON e.ManagerID = m.ManagerID
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