Let us continue our question of the day series with day nine.

Where does referential integrity mean?

Referential integrity means that when a table references another table the foreign key must always point to a real and valid row in the corresponding table.  In other words, if you have an order table and an order line item table and you delete the order table, there should not be an order line item records for that order.  Referential integrity ensures that those related records are update or deleted accordingly.  The tables are in essence synchronized.

Enjoy!