天生舞男

我喜欢谦虚的学习各种...,希望自己能坚持一辈子,因为即使一张卫生巾也是有它的作用.
posts - 76, comments - 39, trackbacks - 1, articles - 4
  博客园 :: 首页 :: 新随笔 :: 联系 :: 订阅 订阅 :: 管理

公告

多个平均数列的子查询

Posted on 2008-01-09 18:08 天生舞男 阅读(...) 评论(...) 编辑 收藏
SELECT company_name, title, teachername, company.id,average
    FROM companies company
    left outer join (select ROUND(avg(score), 2) as average, company_id
       from companycomments
       group by company_id) companycomments
    on company.id = companycomments.company_id
    left outer join
    (
     select company_id, title,teachername
     from trainings, teachers, teachers_trainings
     where teachers.id = teachers_trainings.teacher_id
           and teachers_trainings.training_id = trainings.id
    ) totalInfo
    on company.id = totalInfo.company_id