SELECT employee_id,last_name,department_name,city FROM employees e, departments d, locations l WHERE e.department_id=d.department_id AND d.location_id=l.location_id; #非等值连接 SELECT * FROM job_grades; #举例: 查询名字、月薪和对应的等级 SELECT e.last_name,e.salary,j.grade_level FROM employees e,job_grades j WHERE e.salary BETWEEN j.lowest_sal AND j.highest_sal; SELECT * FROM employees; SELECT e.last_name,e.salary,j.grade_level FROM employees e,job_grades j WHERE e.salary >= j.lowest_sal AND e.salary