Home/ Questions/Q 452453
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-12T22:04:27+00:00

As I understood from this post , there are some scenarios where foreign keys

  • 0

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 referential integrity checks, foreign keys can actually hurt query performance. Under which conditions (if at all) is this true?

1) The term query seems to be misleading. I am interested in all kinds of performance penalties.

2) Does anyone have any real-world numbers about the negative impact on INSERT, DELETE or UPDATE statements (I know it depends on the specific system, but nevertheless any kind of real-world measurements would be appreciated)?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    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.)

    • 0