Question

how do you change the relationship between two tables to a many to many to many relationship in sql. Im using oracle for the DB.

thanks

Answer 1

Relationships among tables are almost always, ONE-TO-MANY, or ONE-TO-ONE. There is no MANY-TWO-MANY relationship between two tables. If you want a MANY-TO-MANY you will need to create intermediate relation to hold the relationship.

For example, if you want a MANY-TO-MANY relationship between table A and B you will need to create an intermediate table C:

create table a (a_id number primary key);
create table b (b_id number primary key);
-- c will hold many-to-many relationship between a and b
create table c (
    a_id number not null references a(a_id),
    b_id number not null references b(b_id),
    primary key(a_id, b_id)
);