Relational database model
The relational model is today the primary data model for commercial data processing applications. It has attained its primary position because of its simplicity, which eases the job of the programmer, as compared to earlier data models such as the network model or the hierarchical model.
A database based on the relational model developed by E.F. Codd allows the definition of data structures, storage and retrieval operations and integrity constraints. In such a database the data and relations between them are organized in tables. A table is a collection of records and each record in a table contains the same fields. Properties of Relational Tables are:
- Values are Atomic
- Each row is unique
- Column values are of the same kind
- The sequence of columns is insignificant
- The sequence of Rows is insignificant
- Each column has a unique name
It is a most common database model for new systems. This model defines simple tables for each relation and many-to-many- relationship. Cross reference keys link the tables together, representing the relationships between entities. Primary and secondary key indexes provide rapid access to data based upon qualifications. Most new applications are built using relational DBMSs, and many relational DBMS products exist.
In relational data model, the database is represented as a group of related tables. The relational data model was introduced in 1970. It is currently the most popular model. The mathematical simplicity, and ease of visualization of the relational data model, has contributed to its success. The relational data model is based on the mathematics of set theory.
Advantages of Relational Model:
a) Since one table is linked with other with some common fields, rules implemented on one table can easily be implemented to another.
b) Some rules, popularly known as referential integrity, can easily be implemented.
c) Very less redundancy.
d) Normalization of database is possible.
e) Rapid database processing is possible.
Disadvantages of Relational Model:
a) It is more complex than other models.
b) Too many rules makes database non-user-friendly