通过外键连接的另一个表的参考数据

Question

I'm building a social site in which each user belongs to a particular group. The home page (the "news feed", so to speak) displays recent posts from anyone within their group. Therefore, I need to grab any stories from people that match the group ID of the logged-in user.

The stories table contains several columns, one of which is poster_id (which is FK constrained to the ID column in the users table), and the user table also has a column group_id. Essentially, what I need to do is this:

SELECT * FROM stories WHERE poster_id.group_id = '$logged_in_user_group'

But obviously I can't just directly reference group_id by going through poster_id. What would be the simplest way to kind of "backtrack" into the users table, so I can compare the group_id?

Answer 1

You are looking for a "join":

select stories.*
from stories
join poster on poster.poster_id = stories.poster_id
where poster.group_id = '$logged_in_user_group'