Question

should we always combine one-to-one tables?

I have a user id uid, a table containing the basics:

uid, name, address, etc..

and another table that is essentially the same thing, with the foreign key on the previous user table

uid, stats, etc..

should i just combined them? when does it make sense to and when would i not want to?

Answer 1

Check out this resource on the Five Normal Forms for Relational Databases. In it you will find some guidelines for deciding how to combine information or split it out into tables.

In a nutshell, use this rule of thumb:

• Each table should represent one type of thing.
• The primary key should uniquely distinguish that thing from other items in the table.
• Every column in the table should depend on the primary key value and only the primary key value.
  • If multiple fields in a single table form a logical sub-group (for example parts of an address), then they probably deserve their own table.