# 1965. 丢失信息的雇员
# https://leetcode-cn.com/problems/employees-with-missing-information/

# SQL架构
Create table If Not Exists Employees (employee_id int, name varchar(30));
Create table If Not Exists Salaries (employee_id int, salary int);
Truncate table Employees;
insert into Employees (employee_id, name) values ('2', 'Crew');
insert into Employees (employee_id, name) values ('4', 'Haven');
insert into Employees (employee_id, name) values ('5', 'Kristian');
Truncate table Salaries;
insert into Salaries (employee_id, salary) values ('5', '76071');
insert into Salaries (employee_id, salary) values ('1', '22517');
insert into Salaries (employee_id, salary) values ('4', '63539');

# Write your MySQL query statement below
select
    employee_id
from
    (
        select
            employee_id
        from
            Employees
        union
        all
        select
            employee_id
        from
            Salaries
    ) as employee_id
group by
    employee_id
having
    count(employee_id) = 1
order by
    employee_id;

# clean-up
drop table Employees;
drop table Salaries;