MySQL 多表连接

Question

我需要修改以下 MySQL 语句以包含来自第三个表的信息...但我不擅长连接。

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

我还需要通过将 searches.project_id 与 projects.id 匹配来检索 projects.project_name。

Answer 1

查看 SELECT Syntax和 JOIN Syntax .

但是，最简单的答案——添加另一个 JOIN..ON 语句。

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

[EDIT] 我添加了 -- + 注释以指出我的添加。