Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Integrity constraints are used to ensure accuracy and consistency of data in a relational database. Data integrity is handled in a relational database through the concept of referential integrity. There are many types of integrity constraints that play a role in referential integri ...Full description
Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Integrity constraints are used to ensure accuracy and consistency of data in a relational database. Data integrity is handled in a relational database through the concept of referential integrity. There are many types of integrity constraints that play a role in referential integrity.Codd, initially defined two sets of constraints, but in his second version of the relational model, he came up with five integrity constraints. The entity integrity constraint states that no primary key value can be null. This is because the primary key value is used to identify individual tuples in a relation . Having null value for the primary key implies that we cannot identify some tuples.