#案例：选中city在多伦多工作的员工

SELECT last_name,job_id,e.department_id,department_nameFROM employees AS e,departments AS d,locations AS lWHERE e.`department_id`=d.`department_id`AND d.`location_id`=l.`location_id`AND l.city='Toronto'

#案例；查询每个国家下的部门个数大于2的国家编号

SELECT country_id ,COUNT(*)FROM locations AS l,departments AS dWHERE l.`location_id`=d.`location_id`GROUP BY country_idHAVING COUNT(*) >2;