RDBMS

What is RDBMS?

 

In this article we will learn about RDBMS.

RDBMS – Relational Database Management System, is a software system or collection of various programs that work together on a relational datamodel database and offer various integrated entities like – Database administration, Data definition, creation, updation etc. Some examples of RDBMS are –

  • SQL
  • mySQL
  • IBM DB2
  • Oracle
  • Microsoft Access

RDBMS was introduced by E. F. Codd.

The basic structure of RDBMS revolves around tables like –

RDBMS

Table

The data in RDBMS systems are stored inside tables.

    • In the first row, each column contains the attribute names of an entity
    • The next set of rows contain the data for an entity set object
Table in RDBMS

Record or Row

The each row containing the data about a single entity in the entity set is called the record. This is also known as tuple as well.

Example –

For students studying in a university the entity is student and information about roll number 1 is stored in the a row which has values of all information like name, age, gpa year etc.

Column or Attribute

Column is all the values for a particular attribute for a table. This information is stored vertically.

For example – for students all the names as shown in the image will be the column.

Column

Field

Fields are nothing but the list of all possible attributes for the table. Roll_No, name, age, GPA, year all are fields.

Field

SQL Constraints

Constraints in DBMS are various checks invoked by the system before an entry in a record. If it doesn’t match in that case data won’t be entered in the record itself. It is essential to maintain the integrity, authenticity and also sometimes security of the database.

The following are some constraints in SQL –

  • Default
  • Not Null
  • Unique
  • Check
  • Key Constraints
  • Domain constraints
  • Mapping constraints

We will learn more about them in detail in further posts-

We will learn also about –

  • Data Normalisation
  • Various SQL Queries
  • Various Joins
  • Relational Algebra
  • Relation calculus
  • Data Integrity