> Say I have a "user" table that has first, last, email, password, and
> last_accessed columns. This user table will be accessed often. (It's
> not really "user", but that's not important in this discussion)
>
> Say that there's also about 10 columns of settings or preferences for
> each user. Are there any cases or reasons to have a separate
> "user_preferences" table vs. just placing all the columns together in
> one table?
I did something like that on MySQL some time ago.
In the Users table there was stuff that other users need to see (like his
login name, etc), and stuff that only this user needs to see (like his
preferences).
So, when displaying posts in the forum, for instance, only a small part
of the fields in the Users table was needed, the rest was just dead
weight, that made the table unable to fit in RAM.
So I split the table, and it was faster.
However, you can also buy more RAM...