day2 employees whose income exceeds the manager's income

This question uses MySQL 8.0 and has not been tested in MySQL 5.6, so it is not guaranteed to be correct.

topic

Topic source: income exceeds the manager's income 161e8d7428b13b

Managers are also employees. Each employee has an Id, in addition to a column of Id corresponding to the employee's manager. Look up the names of employees who earn more than their managers

create table employee (
    id int,
    name varchar(255),
    salary int,
    managerId int
);

insert into employee values 
(1, 'Joe', 70000, 3),
(2, 'Henry', 80000, 4),
(3, 'Sam', 60000, null),
(4, 'Max', 90000, null);

SQL

select employee.name from employee left join employee e
on employee.managerId = e.id
where employee.salary > e.salary;

Parse

managerId is the manager id , and the manager is also an employee, that is to say, no managerId is an ordinary employee, and managerId is a manager.

Therefore, employee self-connected, and the connection condition is employee.managerId = e.id , and ordinary employees and managers can be connected.

Then filter out the employees employee.salary > e.salary

More reference for solving problems: https://github.com/astak16/blog-mysql