What are foreign key constraints in databases?

What are foreign key constraints in databases?

Foreign key constraints are rules that maintain referential integrity between tables in a database.

Can you explain how they work with an example?

Sure! If you have a 'Customers' table and an 'Orders' table, a foreign key in 'Orders' can reference the 'CustomerID' in 'Customers'.

What happens if I try to delete a customer who has orders?

If you try to delete that customer, the database will prevent it unless you first delete the related orders, unless you have set up cascading deletes.

Are there any performance implications of using foreign key constraints?

Yes, while they help maintain data integrity, they can slow down insert and update operations due to the additional checks.