如何从 2 个表中获取每个部门的最高薪水 - sql？

Question

我有 2 张桌子，部门和员工。我需要获取每个部门最高薪水的员工姓名。

create table Dep(name_dep char, id_dep int);

insert into Dep values("econ", 1);
insert into Dep values("credit", 2);
insert into Dep values("energy", 3);
insert into Dep values("retail", 4);
insert into Dep values("manufactury", 5);

create table Emp(id_emp int, id_dep int, age int, person_name char, salary int );
insert into Emp values(1, 1, 23, 'john', 200);
insert into Emp values(3, 2, 3, 'dalbai', 100);
insert into Emp values(6, 3, 53, 'borat', 300);
insert into Emp values(7, 1, 63, 'erjan', 1600);
insert into Emp values(9, 2, 73, 'sergey', 1000);
insert into Emp values(8, 5, 83, 'lucy', 20);
insert into Emp values(90, 4, 93, 'mike', 1200);

如何查询各部门最高工资的员工姓名？ 我的查询：

SELECT person_name, name_dep
FROM Emp e
INNER JOIN
(
    SELECT name_dep, MAX(salary) AS max_salary
    FROM Dep d
    GROUP BY id_dep
) d
    ON e.id_dep = d.id_dep

Answer 1

加入表和返回每个部门最高薪水的查询：

select
  d.name_dep, e.person_name, t.salary
from Dep d inner join (
  select id_dep, max(salary) salary
  from Emp
  group by id_dep
) t on t.id_dep = d.id_dep
inner join Emp e on e.id_dep = t.id_dep and e.salary = t.salary

请参阅demo。
结果：

| name_dep    | person_name | salary |
| ----------- | ----------- | ------ |
| energy      | borat       | 300    |
| econ        | erjan       | 1600   |
| credit      | sergey      | 1000   |
| manufactury | lucy        | 20     |
| retail      | mike        | 1200   |

Answer 2

虽然我已经纠正了 Gordon 的回答，但是如果您严格需要 ANCI 方法，您可以使用以下查询 -

SELECT e.person_name, d.name_dep, d.max_salary
FROM Emp e
INNER JOIN Dep d ON e.id_dep = d.id_dep
INNER JOIN (SELECT id_dep, MAX(salary) AS max_salary
            FROM Emp
            GROUP BY id_dep) d ON e.id_dep = d.id_dep
                               AND e.salary = d.max_salary

基本上您使用的是 name_dep 而不是我已更正的 id_dep。

Answer 3

我有一个表，其工作方式与您的表几乎相同，在该表中我使用相关子查询

select * from emp inner join dept on emp.deptno = dept.deptno where 
(emp.deptno, sal) in 
(select deptno, max(sal) from emp where deptno = emp.deptno 
group by emp.deptno);

相关查询获取更高的薪水和部门分组，然后，外部查询使用结果作为条件从表中提取信息，我喜欢它有帮助

Answer 4

使用窗口函数。对于一个人，使用row_number()：

SELECT person_name, name_dep
FROM (SELECT e.person_name, d.name_dep,
             ROW_NUMBER() OVER (PARTITION BY e.id_dep ORDER BY e.salary DESC) as seqnum
      FROM Emp e INNER JOIN
           Dep d
           ON e.id_dep = d.id_dep
     ) ed
WHERE seqnum = 1;

如果您想在平局的情况下使用所有重复项，请使用RANK()。