员工数据库的 SQL 查询

Question

我是 SQL 的新手，这学期我正在上数据库类(class)。我有大约 20 个查询要在这个数据库上尝试，其中有两个我无法弄清楚...我想知道这里是否有人能够提供帮助!

这是我已经创建的表格。

create table employee(
  EID varchar(20) primary key,
  Lastname varchar(20),
  Firstname varchar(20),
  Midinitial char(1),
  gender char(1),
  street varchar(20),
  city varchar(20)
);

create table works(
  EID varchar(20) primary key,
  Lastname varchar(20),
  Firstname varchar(20),
  Midinitial char(1),
  company_name varchar(20),
  salary numeric(5,0),
  foreign key(EID) references employee,
  foreign key(company_name) references company
);

create table company(
  company_name varchar(20) primary key,
  city varchar(20)
);

create table manages(
  EID varchar(20) primary key,
  Lastname varchar(20),
  Firstname varchar(20),
  Midinitial char(1),
  ManagerLastname varchar(20),
  MFirstname varchar(20),
  MMidinitial varchar(20),
  start_date date,
  foreign key (EID) references employee
);

找出为第一银行工作并住在奥马哈的所有经理的薪水。

这是我对这个的看法，我认为它是正确的，但我不想回答这个问题，直到我也能得到第二个......

select distinct salary
from employee, works, manages
where employee.city = 'Omaha' 
  and works.company_name = 'First Bank' 
  and manages.managerlastname = employee.Lastname
  and employee.EID = works.EID

和

找出所有员工中工资最高的员工的姓名和公司名称。

Answer 1

我很确定它应该是:

SELECT w.salary FROM works w INNER JOIN employee e ON w.EID = e.EID
 WHERE e.city = 'Omaha' AND w.company_name = 'First Bank' AND EXISTS
 ( SELECT * FROM managers m WHERE m.EID = w.EID);

第二个:

SELECT e.Firstname, e.Lastname, w.company_name FROM employee e INNER JOIN
  works w ON e.EID = w.EID ORDER BY w.salary DESC LIMIT 1;