What Is a Cost-Based Optimizer?

When you execute a query, the database server has to figure out things like:

Which table to process first Which index to use on that table Whether to seek on that index or scan it Which table to process next How to join the data between those two tables When to sort the data

For even the simplest queries, there are usually several possible ways to get the job done. The database server has to figure out which way is going to be the fastest – or at least, fast enough for the meatbag who ran it.

One way to