使用不同表上的查询过滤查询结果

此查询选择不在 Supervisors 表上的所有员工。

SELECT *
FROM Employees
WHERE EmployeeID not in (SELECT EmployeeID
                            FROM Supervisors)

使用 LEFT JOIN 可以获得相同的结果。

SELECT *
FROM Employees AS e
LEFT JOIN Supervisors AS s ON s.EmployeeID=e.EmployeeID
WHERE s.EmployeeID is NULL