Relational data model:


 

  • There is one data structure, the relation, which is defined in terms of attributes, tuples, primary keys, foreign keys and domains.



  • Data is manipulated by a non-procedural language (SQL), a table at a time.



  • There are two inherent integrity rules: entity and referential integrity.


Network data model:


 

  • The data is defined as record types and set types.



  • Data manipulation is by a series of database specific functions embedded in some host language.



  • There is automatic support for certain forms of referential integrity.


In terms of the relational model, describe the following:


 

Data definition


 

  • In the relational model there is only one data structure, the relation.



  • A relation is a table which is defined in terms of attributes, tuples, primary keys, foreign keys and domains.


Data Manipulation


 

  • Data manipulation is conducted using a series of eight operators – relational algebra.



  • The main operators are restrict, project and join. Others are product, union, intersection, difference and division.


Data Integrity


 

  • Data integrity is enforced via the entity and referential integrity rules.



  • These two rules are inherent since every relational database should demonstrate adherence to these two rules.