1. make it diﬃcult to insert invalid or inconsistent data  2. on inserting/updating/deleting an item, automatically enforce logical relationships throughout database
1. make it diﬃcult to insert invalid or inconsistent data  2. on inserting/updating/deleting an item, automatically enforce logical relationships throughout database
in a database or a collection of databases, the condition that exists when data values are consistent and in agreement with one another.