Friday, October 12, 2012

Relational Database Management System(RDBMS) Overview and Properties

RDBMS (Relational Database Management System):

This model was developed by a German scientist Mr. EF.Codd in 1970.He developed this model on the basis of a mathematical concept name is known as relational algebra.
Relations are classified into three types.

1) One-One : One object can have relationship with only one object


2) One-Many/Many-One : One object can have many relationships with different objects and vice versa.

3) Many-Many : Many objects can have relationship with many objects.

Properties Of RDBMS :

  • Data should be stored in the form of tables.
  • A table can be defined as collection of rows and columns.
  • Table is also called as Entity (or) Object.
  • The horizontal lines are called as rows (or) records (or) tuples.
  • The vertical lines are called as columns (or) fields (or) attributes.
  • The intersection of row and column is known as cell. A cell is a place where we can store the data.
Properties of Table :

Table should not contain duplicate columns. While inserting the records into the tables user no need to follow any order. When we define the columns in the table user no need to follow any specific order.

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