相关子查询的外部查询的多个结果

Question

我想知道是否可以让内部查询 return 多个结果然后由外部查询查询？

这是一个可重现的例子：

在这个例子中，我想知道每个部门薪酬最高的员工的姓名和薪水。

CREATE TABLE Worker (
    WORKER_ID INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
    FIRST_NAME CHAR(25),
    LAST_NAME CHAR(25),
    SALARY INT(15),
    JOINING_DATE DATETIME,
    DEPARTMENT CHAR(25)
);

INSERT INTO Worker 
    (WORKER_ID, FIRST_NAME, LAST_NAME, SALARY, JOINING_DATE, DEPARTMENT) VALUES
        (001, 'Monika', 'Arora', 100000, '14-02-20 09.00.00', 'HR'),
        (002, 'Niharika', 'Verma', 80000, '14-06-11 09.00.00', 'Admin'),
        (003, 'Vishal', 'Singhal', 300000, '14-02-20 09.00.00', 'HR'),
        (004, 'Amitabh', 'Singh', 500000, '14-02-20 09.00.00', 'Admin'),
        (005, 'Vivek', 'Bhati', 500000, '14-06-11 09.00.00', 'Admin'),
        (006, 'Vipul', 'Diwan', 200000, '14-06-11 09.00.00', 'Account'),
        (007, 'Satish', 'Kumar', 75000, '14-01-20 09.00.00', 'Account'),
        (008, 'Geetika', 'Chauhan', 90000, '14-04-11 09.00.00', 'Admin');

找到每个部门的最高薪水很容易：

SELECT MAX(SALARY), DEPARTMENT
FROM Worker
GROUP BY DEPARTMENT;

但是我如何将赚取这些薪水的员工的姓名也添加到结果中？

非常感谢！

Answer 1

您可以将查询与运算符 IN:

结合使用

SELECT * FROM Worker
WHERE (DEPARTMENT, SALARY) IN (
  SELECT DEPARTMENT, MAX(SALARY) 
  FROM Worker
  GROUP BY DEPARTMENT 
);

或者如果您使用 MySql 8.0+ 和 RANK() window 功能：

SELECT w.* 
FROM (
  SELECT *, RANK() OVER (PARTITION BY DEPARTMENT ORDER BY SALARY DESC) rnk
  FROM Worker
) w
WHERE w.rnk = 1

参见demo。
结果：

> WORKER_ID | FIRST_NAME | LAST_NAME | SALARY | JOINING_DATE        | DEPARTMENT
> --------: | :--------- | :-------- | -----: | :------------------ | :---------
>         3 | Vishal     | Singhal   | 300000 | 2014-02-20 09:00:00 | HR        
>         4 | Amitabh    | Singh     | 500000 | 2014-02-20 09:00:00 | Admin     
>         5 | Vivek      | Bhati     | 500000 | 2014-06-11 09:00:00 | Admin     
>         6 | Vipul      | Diwan     | 200000 | 2014-06-11 09:00:00 | Account

相关子查询的外部查询的多个结果

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correlated-subquery