Can foreign keys hurt query performance

Question

As I understood from this post, there are some scenarios where foreign keys can improve query performance.

I\'ve heard the opposite claim though, that because of refere

Answer 1

I'm assuming that for INSERT queries, constraints - including foreign key constraints - will slow performance somewhat. The database has to check that whatever you've told it to insert is something that your constraints allow it to insert.

For SELECT queries, foreign key constraints shouldn't make any changes to performance.

Since INSERTS are almost always very quick, the small amount of extra time won't be noticeable, except in fringe cases. (Building a several gigabyte database, you might want to disable constraints and then re-enable later, as long as you're sure the data is good.)