MySQL多表联接 | MySQL多表联接

本文介绍了MySQL多表联接的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我需要修改以下MySQL语句以包含来自第三张表的信息...但是我很迷恋联接.

I need to modify the following MySQL statement to include information from a third table... but I suck at joins.

select
    ss.*,
    se.name as engine,
    ss.last_run_at + interval ss.refresh_frequency day as next_run_at,
    se.logo_name
from
    searches ss join search_engines se on ss.engine_id = se.id
where
    ss.user_id='.$user_id.'
group by ss.id
order by ss.project_id, ss.domain, ss.keywords

我还需要包括通过将searches.project_id与projects.id匹配来检索projects.project_name.

I need to also include retrieving projects.project_name by matching searches.project_id to projects.id.

推荐答案

查看 SELECT语法和 JOIN语法.

Check out SELECT Syntax and JOIN Syntax.

但是，最简单的答案-添加另一个JOIN..ON语句.

But, simplest answer -- add another JOIN..ON statement.

select
        ss.*,
        se.name as engine,
        ss.last_run_at + interval ss.refresh_frequency day as next_run_at,
        se.logo_name,
        pr.project_name -- +
from
        searches ss
        join search_engines se on ss.engine_id = se.id
        join projects pr on ss.project_id = pr.id -- +
where
        ss.user_id='.$user_id.'
group by ss.id
order by ss.project_id, ss.domain, ss.keywords

[编辑]，我添加了-- +注释以指出我的添加内容.

[EDIT] I added the -- + comments to point out my additions.

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