Subquery vs Join Performance: Which is Better?

What's the difference in performance between subqueries and joins in SQL?

Subqueries and joins serve different purposes. Joins combine rows from two or more tables based on a related column, while subqueries are nested queries that can be used to filter results. Performance can vary based on the database and the specific query.

In what scenarios would a subquery perform better than a join?

Subqueries can perform better when you need to filter results based on aggregated data or when dealing with complex conditions that are easier to express in a subquery.

Are there any general rules for optimizing SQL queries involving joins and subqueries?

Yes, some general rules include using indexes, avoiding unnecessary columns in SELECT statements, and considering the execution plan to identify bottlenecks.

Can you give me an example of a subquery that performs well?

Sure! For instance, if you want to find customers who have placed orders above a certain amount, a subquery can efficiently filter those customers based on the aggregated order total.