I have two distinct scenarios.
One, where there is a many to many case, you must create a third table. But I'm not familiar with MySQL syntaxis.

Two, is this one:

How can I declare using SQL code?
I have two distinct scenarios.
One, where there is a many to many case, you must create a third table. But I'm not familiar with MySQL syntaxis.

Two, is this one:

How can I declare using SQL code?
In MYSQL my create tables using the CREATE TABLE command. If you don't feel too confident to write your tables with that syntax, I'd suggest using a tool like the MySQL Workbench. That tool can greatly help you there.