where can I learn more about MySQL Relations (1:1,1:m,etc) in an easy-to-understand fashion?

Question

I understand about JOINS, but what exactly is the whole point of relations? I don't "get" it. Probably because all the material available asume you know MySQL almost as well as the people that wrote it...

Answer 1

Imagine a Customer table. This table has details of a person. The table will also contain a foreign key field to the Address table.
The Address table will contain a unique key plus details of the address.

If you have two different customers living at the same address then this is not a problem because the different Customer rows just have the same Address key.
So for 1 Address you have many Customers.
For 1 Customer you have 1 Address.

That is all that this means.