Total Beginner Question

Anon

Ok I'm very new to php and MySQL, Here is my question.

When developing database driven web pages and PHP applications does it require you to have more than one database? My host will allow me 3 MySQL databases, Is this enough? or do I need a database for each application I develop?

Anon

You should look at a MySQL database as a placeholder for tables. You can have an infinite amount of tables within your database.

Normally, people use different databases to organize their data efficiently... however it's not a requirement.

Having 3 databases should be more than adequate for one database driven website. Just remember to choose your tables carefully, and index all of them (no matter what you're storing). (indexing means having a primary key in each table)

[deleted]

Indexing means slightly more than just creating a primary key...

It's very important to properly normalize your tables. Creating a primary key is part of that.
Indexes just help the database to quickly find the dat you need.
Use the EXPLAIN command in SQL to let SQL show you which indexes (if any) it used to get your data. If no indexes were used, you either have a query that can't use indexes, or you have too few/the wrong indexes.