Entity integrity

Entity integrity

In the relational data model, entity integrity is one of the three inherent integrity rules. Entity integrity is an integrity rule which states that every table must have a primary key and that the column or columns chosen to be the primary key should be unique and not null [Beynon-Davies P. (2004). Database Systems 3rd Edition. Palgrave, Basingstoke, UK. ISBN 1-4039-1601-2] .A direct consequence of this integrity rule is that duplicate rows are forbidden in a table. If each value of a primary key must be unique no duplicate rows can logically appear in a table. The NOT NULL characteristic of a primary key ensures that a value can be used to identify all rows in a table.

Within relational databases using SQL, entity integrity is enforced by adding a primary key clause to a schema definition.The system enforces Entity Integrity by not allowing operations (INSERT, UPDATE) to produce an invalid primary key. Any operation that is likely to create a duplicate primary key or one containing nulls is rejected.

References

ee also

*Relational Database Management System
*Structured Query Language (SQL)
*Referential integrity


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