I am trying to figure out how to structure this database. I have used Apple's core data before just fine, I'm just working on a different project now that requires MySQL. I am very new to MySQL so please go easy on me. :)
For this example, let's say I have three tables, User, Device, and Location. Drawing it out, a Location can have many Devices, but the Device can only have one Location; Each User has its primary key, UserID, of which I need to use to fetch the correct information.
So how do I create a relationship like this here? I've heard of creating an index and a foreign key and I'm not sure how they work exactly.
In the end, what I need to do is be able to access the User's specific table and view all of the Locations associated with that User. I will also need to be able to add a Device at a certain Location for a certain User.
Again, please forgive me as I'm trying to wrap my head around MySQL. I am using HeidiSQL to do my database editing.
User - Device is a many-to-many relationship, so you'll want to introduce an intermediary table to resolve that relationship. That table simply consists of two foreign keys, one referencing the User table and one referencing Device. Device - Location can be handled with a simple foreign key in the Device table pointing to a Location table.
来源：https://stackoverflow.com/questions/8216865/mysql-relationships