如何在mysql中创建具有多个表的关系？

Question

What I'm doing now, possibly mistaken:

users:
id,name

actions:
id, user_id

events:
id, action_id, description

posts
id, event_id, text

What I would like:

A User can create many actions.

An Action can have one Event

An Event can have many posts, but should be related to just one Event

The "trick" is I want that my Actions to have many posts, so I assume that creating the Event table was right.

What kind of relation should be set up assuming this?

Answer 1

Since An Action can have many posts but should be related to just one Event , this is a simple join.

SELECT users.*, actions.*, events.*, posts.* FROM users 
LEFT JOIN actions ON users.id = actions.user_id 
LEFT JOIN events ON actions.id = events.action_id
LEFT JOIN posts ON events.id = posts.events_id

As mentioned in the comment above, there is not a need for the events table if an action is only ever going to have only 1 event AND the event is unique to that action - meaning the event won't be used in the future by another action.

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Regarding you comment above that An Action can have many posts but should be related to many Events , this wouldn't change the join.