LeetCode 1303. Find the Team Size

Description

https://leetcode.com/problems/find-the-team-size/

SQL Schema

Table: Employee

+---------------+---------+
| 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:

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.

Explanation

JOIN on tables after GROUP BY and COUNT

SQL Solution

# Write your MySQL query statement below
select Employee.employee_id, team_size from Employee join 
(select *, count(*) as team_size from Employee group by team_id) t on Employee.team_id = t.team_id

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