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Compare the relational data model to the network data model.

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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.
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