LeetCode（数据库）- 丢失信息的雇员

-- 解决方案(1)
with t as  (
select employee_id  from Employees
union all
select employee_id  from Salaries)
select employee_id from t
group by employee_id
having count(employee_id)=1
order by employee_id
-- 解决方案(2)
WITH t AS (SELECT employee_id FROM Employees
UNION 
SELECT employee_id FROM Salaries)
SELECT * 
FROM t
WHERE employee_id NOT IN (SELECT e.employee_id FROM Employees e JOIN Salaries s USING(employee_id))
ORDER BY employee_id