I have a large database, one of the tables is called Users.
There are two kinds of users in the database – basic users, and advanced users. In the users table, there are 29 columns. However, only 12 of these are applicable to the basic users – the other 17 columns are only used for advanced users, and for basic users they all just contain a value of null.
Is this an OK setup? Would it be more efficient to, say, split the two kinds of users into two different tables, or put all the extra fields that advanced users have in a separate table?
It’s better to have the right amount of tables – this may be more or less, depending on your needs.
To your specific case, you should always start with third normal form and only revert to lesser forms when absolutely necessary (such as for performance) and only when you understand the consequences.
An attribute (column) belongs in a table if it is dependent on the key, the whole key and nothing but the key (so help me, Codd).
It’s arguable whether your other 17 columns depend on the key in your user table but I would be separating them anyway just for the space saving.
Have your basic user table with the twelve columns (including a unique key of some sort) and your advanced user table with the other columns, and also that key so you can tie the rows from each together.
You could go even further and have a one to many relationship if your use case is that users can have any of the 17 attributes independent of each other but that doesn’t seem to be what you’ve described.