1、題目描述
Write an SQL query that reports all the projects that have the most employees.
The query result format is in the following example:
Project table:
| project_id | employee_id |
|---|---|
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
| 2 | 1 |
| 2 | 4 |
Employee table:
| employee_id | name | experience_years |
|---|---|---|
| 1 | Khaled | 3 |
| 2 | Ali | 2 |
| 3 | John | 1 |
| 4 | Doe | 2 |
Result table:
| project_id |
|---|
| 1 |
The first project has 3 employees while the second one has 2.
來源：力扣（LeetCode）
2、解題思路
1# 主要是解決，出現多個最大值的情況
2# 首先增加子表，使用倒序和限制數量組合，得出最大值group by project_id order by count(employee_id) desc limit 1
select count(employee_id)
from Project
group by project_id
order by count(employee_id) desc
limit 1
3# 然後，直接讓count(employee_id)等於上述值就行了
3、提交記錄
select project_id
from Project
group by project_id
having count(employee_id)=
(select count(employee_id)
from Project
group by project_id
order by count(employee_id) desc
limit 1 )