哈

SELECT first_name, last_name,department_name
FROM employees,departments
where employees.department_id=departments.department_id;

SELECT e.employee_id,e.last_name,d.department_name,l.city
FROM employees e,departments d,locations l
WHERE e.department_id=d.department_id
AND d.location_id=l.location_id;

SELECT * FROM job_grades;

#查询名字，月薪和对应的等级
SELECT last_name,salary,grade_level
FROM employees,job_grades
WHERE employees.salary BETWEEN job_grades.lowest_sal AND job_grades.highest_sal;

SELECT last_name,salary,grade_level
FROM employees,job_grades
WHERE employees.salary>=job_grades.lowest_sal
AND employees.salary<=job_grades.highest_sal;

#角度二
SELECT * FROM employees;

SELECT emp.employee_id,emp.last_name,mgr.employee_id,mgr.last_name
FROM employees emp,employees mgr
WHERE emp.manager_id=mgr.employee_id;