Should I use one big SQL Select statement or several small ones?

Question

I\'m building a PHP page with data sent from MySQL.

Is it better to have

• 1 SELECT query with 4 table joins, or
• 4 small SELE

Answer 1

When you use JOINs instead of multiple queries, you allow the database to apply its optimizations. You also are potentially retrieving rows that you don't need (if you were to replace an INNER join with multiple selects), which increases the network traffic between your app server and database server. Even if they're on the same box, this matters.