Managers with at Least 5 Direct Reports

Author: Viniciuscoding

Leetcode_570.sql

@@ -0,0 +1,44 @@
+/*
+Managers with at Least 5 Direct Reports
+
+The Employee table holds all employees including their managers. Every employee has an Id, 
+and there is also a column for the manager Id.
+
++------+----------+-----------+----------+
+|Id    |Name 	    |Department |ManagerId |
++------+----------+-----------+----------+
+|101   |John 	    |A 	        |null      |
+|102   |Dan 	    |A 	        |101       |
+|103   |James 	  |A 	        |101       |
+|104   |Amy 	    |A 	        |101       |
+|105   |Anne 	    |A 	        |101       |
+|106   |Ron 	    |B 	        |101       |
++------+----------+-----------+----------+
+Given the Employee table, write a SQL query that finds out managers with at least 5 direct report. For the above table, 
+your SQL query should return:
+
++-------+
+| Name  |
++-------+
+| John  |
++-------+
+Note:
+No one would report to himself.
+*/
+
+# MY SOLUTION (Faster)
+SELECT Name
+FROM Employee
+WHERE Id IN (SELECT ManagerId
+             FROM Employee
+             WHERE ManagerId IS NOT null
+             GROUP BY ManagerId
+             HAVING COUNT(ManagerId) >= 5)
+
+# MY SOLUTION (Slower)
+SELECT m.Name
+FROM Employee e
+INNER JOIN Employee m
+WHERE e.ManagerId = m.Id
+GROUP BY e.ManagerId
+HAVING COUNT(*) >= 5