LeetCode(184):部門給与が最も高い従業員Reformat Department Table(SQL)

2020.7.8 LeetCode 0ブラシ個人ノートから整理(更新継続)
github:https://github.com/ChopinXBP/LeetCode-Babel
転送ゲート:部門給与が最も高い従業員
Employeeテーブルには、対応するId、salary、department Idを持つすべての従業員情報が含まれています.

+----+-------+--------+--------------+
| Id | Name  | Salary | DepartmentId |
+----+-------+--------+--------------+
| 1  | Joe   | 70000  | 1            |
| 2  | Henry | 80000  | 2            |
| 3  | Sam   | 60000  | 2            |
| 4  | Max   | 90000  | 1            |
+----+-------+--------+--------------+

Departmentテーブルには、会社のすべての部門の情報が含まれています.

+----+----------+
| Id | Name     |
+----+----------+
| 1  | IT       |
| 2  | Sales    |
+----+----------+

SQLクエリーを作成し、各部門で最も給料の高い従業員を見つけます.例えば、上記の表によれば、MaxはIT部門で最高賃金、HenryはSales部門で最高賃金を有する.

+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT         | Max      | 90000  |
| Sales      | Henry    | 80000  |
+------------+----------+--------+

#  ：1.        ；2.               

#       NULL 
SELECT d.Name AS 'Department', t.Name AS 'Employee', t.Salary AS 'Salary'
FROM (
    SELECT e.Name, e.Salary, e.DepartmentId
    FROM (SELECT DepartmentId, MAX(Salary) AS 'maxSalary'
        FROM Employee
        GROUP BY DepartmentId) m, Employee e
    WHERE e.Salary = m.maxSalary AND e.DepartmentId = m.DepartmentId
) t
LEFT JOIN Department d
ON t.DepartmentId = d.Id
WHERE d.Name IS NOT NULL;

#        NULL 
SELECT d.Name AS 'Department', t.Name AS 'Employee', t.Salary AS 'Salary'
FROM (
    SELECT e.Name, e.Salary, e.DepartmentId
    FROM (SELECT DepartmentId, MAX(Salary) AS 'maxSalary'
        FROM Employee
        GROUP BY DepartmentId) m, Employee e
    WHERE e.Salary = m.maxSalary AND e.DepartmentId = m.DepartmentId
) t
INNER JOIN Department d
ON t.DepartmentId = d.Id;

#IN          
SELECT d.Name AS 'Department', e.Name AS 'Employee', e.Salary AS 'Salary'
FROM Employee e
INNER JOIN Department d
ON e.DepartmentId = d.Id
WHERE (e.DepartmentId, e.Salary) IN (
    SELECT DepartmentId, MAX(Salary)
    FROM Employee
    GROUP BY DepartmentId
);

#Coding 1時間、Copying 1秒.いいねを残してくれてありがとう