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SQL 复习一例

爱写作的小土豆 2022-01-15 阅读 109

速查表

在这里插入图片描述

例子

示例表:

/* Employee */
+----+-------+--------+--------------+
| Id | Name  | Salary | DepartmentId |
+----+-------+--------+--------------+
| 1  | Joe   | 70000  | 1            |
| 2  | Henry | 80000  | 2            |
| 3  | Sam   | 60000  | 2            |
| 4  | Max   | 90000  | 1            |
+----+-------+--------+--------------+
/* Department */
+----+----------+
| Id | Name     |
+----+----------+
| 1  | IT       |
| 2  | Sales    |
+----+----------+
SELECT 
    DName AS Department,
    Name AS Employee,
    Salary
FROM (
    SELECT 
        Name, DName, Salary,
        RANK() OVER (PARTITION BY DName ORDER BY Salary DESC) as Ranking
    FROM (
        SELECT * FROM Employee 
        INNER JOIN 
        (SELECT Name AS Dname, Id AS DId FROM Department)
        AS d 
        ON d.DId = Employee.departmentId
    ) as joined
)
AS ranked
WHERE ranked.Ranking = 1;
/* result */
+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT         | Max      | 90000  |
| Sales      | Henry    | 80000  |
+------------+----------+--------+

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