Foreign Keys vs Joins

Is it better to use foreign keys in table开发者_开发问答s or can the same results be achieved with joins?

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Foreign keys are just constraints to enforce referential integrity. You will still need to use JOINs to build your queries.

Foreign keys guarantee that a row in a table order_details with a field order_id referencing an orders table will never have an order_id value that doesn't exist in the orders table. Foreign keys aren't required to have a working relational database (in fact MySQL's default storage engine doesn't support FKs), but they are definitely essential to avoid broken relationships and orphan rows (ie. referential integrity).

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FOREIGN KEYs and JOINs don't do the same thing!

• A FOREIGN KEY enforces data integrity, making sure the data conforms to some rules when it is added to the DB.

• A JOIN is used when you extract/query data from the DB by giving rules how to select the data.

• JOINs work if there are FK or not.

• FK's work if you extract data with or without JOINs.

CONCLUSION: FK and JOIN don't allow you to achieve the same goal!