当前位置:Gxlcms > 数据库问题 > mysql 多表查询案例

mysql 多表查询案例

时间:2021-07-01 10:21:17 帮助过:16人阅读

#案例:选中city在多伦多工作的员工

  1. <code>SELECT
  2. last_name,job_id,e.department_id,department_name
  3. FROM
  4. employees AS e,departments AS d,locations AS l
  5. WHERE
  6. e.`department_id`=d.`department_id`
  7. AND
  8. d.`location_id`=l.`location_id`
  9. AND
  10. l.city=‘Toronto‘</code>

#案例;查询每个国家下的部门个数大于2的国家编号

  1. <code>SELECT
  2. country_id ,COUNT(*)
  3. FROM
  4. locations AS l,departments AS d
  5. WHERE
  6. l.`location_id`=d.`location_id`
  7. GROUP BY
  8. country_id
  9. HAVING
  10. COUNT(*) >2;</code>

mysql 多表查询案例

标签:location   code   from   pre   员工   国家   try   mysql   选中   

人气教程排行