How to set different types of links using Foreign key?

Question

SQL

Well, that is, the standard assignment of a key to a foreign key and the subsequent description of the foreign key results in a 1 to 1 relationship, but how do you make it clear that the relationship is 1 to many or many to many?

Answer 1

In MySQL, the foreign key (Foreign Key) serves only for additional automatic control over the integrity of the database. In a child table, a field cannot take a value that is not included in the list of values ​​of the associated field of the parent table or NULL.
The type of connection in MySQL is not taken into account.