Introduction
Relational database management system (RDBMS) is a popular model used for organizing and managing data. RDBMS stores data in the form of related tables. The relational database management system is the most successful model for providing trustworthy and consistent data storage in corporate environments.
The Relational Model
The relational model was first described by Edgar F. Codd in his paper ‘A Relational Model of Data for Large Shared Data Banks’ in 1970. The paper proposed a mathematical model to describe data and also presented rules regarding the process of accessing of this data. Codd proposed to replace flat files that were used to store data at the time with a database based on relational model.
Database Normalization
Database normalization is the process of organizing data into tables and columns in a way that reduces data redundancy and creates relationships between interdependent data. The relational model is based on the concept of normalization. Normalization uses the concept of relations which can be understood as tables composed of columns (attributes) and rows (tuples).
Boyce-Codd Normal Form (BCNF)
Boyce-Codd Normal Form (BCNF) is a normal form used for ensuring the logical structure of data in a relational database. It is another refinement of the Third Normal Form (3NF) proposed by Codd. The BCNF builds upon the 3NF by establishing a more precise definition of functional dependencies.
Fourth Normal Form (4NF)
Fourth Normal Form (4NF) was proposed by Ronald Fagin in 1977 as an extension to the BCNF. The goal of the 4NF is to ensure the preservation of multivalued dependencies. A table is said to be in 4NF if it satisfies 3NF and all of its non-trivial multivalued dependencies are also satisfied.
Projection
Projection is a relational operation which extracts data from a relation and produces a new relation with only the extracted data. It defines the subset of data from one or more relations with the same attributes or columns in the partially or fully specified relation. It is also used for calculating the aggregate values from the relation. A projection relation may be created from a set of existing relations.
Selection
Selection operation retrieves only those tuples from a relation that satisfies the given condition. The condition is applied on each tuple of the relation individually. It is used to perform the filtering of data.
Join Operation
Join operation is used to combine two relations into one relation by interrelating their attributes. The result of the join operation is a single relation. It is used to combine data from two different relations into a single relation.
Conclusion
The relational database management system is a logical data model that is used for organizing and managing data. The relational model is based on the concepts of normalization and normal forms, Without these fundamental operations the data retrieval process would be much slower and unpredictable. There are several relational operations which are used for extracting, joining or combining data from relations, such as projection, selection and Join operation. These operations are essential for retrieving data from the database efficiently and ensure consistency in the data storage.
