Foreign key based on multiple row ids

Question

I'm trying to figure out how to store a combination of id fields as a foreign key in another table. For example, say TableA has 5 rows -- Ids 1-5.

Without using a comma separated field is there a way I can make rows in TableB based off different combinations of TableA's ids? For example rows[1,3], rows[2,3], rows[1], rows[2,3,4] -- the thing throwing me off is it will always be a variable number of row ids that I am putting together.

Is a comma separated field the only way to accomplish this?

Thanks for any help or pointers...

Answer 1

You're describing a many-to-many relationship between TableA and TableB. You should introduce a third table to resolve this. This new table consists of two foreign keys, one referencing the ID from TableA and one from TableB.