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Aptitude

Relational Data Model

The relational model was first outlined by EF Codd in 1970 and since then it was the most widely used data model and in fact, the only used database management system today in the world

The basic idea between this relational data model is simple two-dimensional tables, also called as relations which consist of rows and columns.

Terms Used in Relational Model
1. Relation:

Representing data in the form of a table consisting of rows and columns and relation both convey the same meaning

Student is a relation which consists of student records.

2. Schema:

Schema is nothing but the organization of data in a table i.e in what order the data is logically aligned

STUDENT relation can be represented as STUDENT (STUD_ID, NAME, PHONE, STATE, STUD_AGE).

3. Instance:

Set of unique values present in the table at present is known as relational instance.

4. Attribute:

An attribute defines the properties of a table that means what type of data that a table is storing ,these are nothing but a view of data in the form of columns

In the relation student STUD_ID, NAME, PHONE, STATE, STUD_AGE correspond to the attributes of the relation.

5. Domain :

A domain is nothing but the set of possible values that are allowed for a column in a database table

For example, the age column in the student table is allowed to have values between 21 -32.

6. Tuple :

It is nothing but the row of the database table

The student relation is having 4 tuples or rows.

7. Null Values :

There are certain situations where data may be unknown, missing or undefined which are represented by using this NULL

A null value is different from zero and any operation on null value will result in null.

Advantages of the relational model

  • Data integrity for accuracy and consistency 
  • No data redundancy 
  • Access control and integrity in the form of constraints which enables validation before entering and accessing the data 
  • Provides high security 
  • Supports to store any types(numbers, characters, date, images, audio, text files )
  • Data can be managed and used by several users at a time 
  • Data can be shared across several platforms.

Note: Oracle 10g, a most popularly used RDBMS is proven to be the fastest database for transaction processing including data warehousing and third-party application on several servers of all sizes.

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