Find The Team Size Problem
Description
LeetCode Problem 1303.
Table: Employee
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+---------------+---------+
| Column Name | Type |
+---------------+---------+
| employee_id | int |
| team_id | int |
+---------------+---------+
employee_id is the primary key for this table.
Each row of this table contains the ID of each employee and their respective team.
Write an SQL query to find the team size of each of the employees.
Return result table in any order.
The query result format is in the following example:
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Employee Table:
+-------------+------------+
| employee_id | team_id |
+-------------+------------+
| 1 | 8 |
| 2 | 8 |
| 3 | 8 |
| 4 | 7 |
| 5 | 9 |
| 6 | 9 |
+-------------+------------+
Result table:
+-------------+------------+
| employee_id | team_size |
+-------------+------------+
| 1 | 3 |
| 2 | 3 |
| 3 | 3 |
| 4 | 1 |
| 5 | 2 |
| 6 | 2 |
+-------------+------------+
Employees with Id 1,2,3 are part of a team with team_id = 8.
Employees with Id 4 is part of a team with team_id = 7.
Employees with Id 5,6 are part of a team with team_id = 9.
MySQL Solution
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select e1.employee_id, count(e2.employee_id) as team_size
from Employee e1
inner join Employee e2 on e1.team_id = e2.team_id
group by e1.employee_id, e2.team_id
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