Introduction to databases

What is database?

Definition of some terms used in database

Data: Data are the facts or figures obtained from various sources.

Information: Information is the processed data.

Table: A database object comprising of related data entries is known as a table. Data present in a table is displayed in the form of rows and columns.

Field: A field is a piece of information about an element which may be a person, student or employee.

Record: A collection of related field is called record.

Cell: A cell is an intersection of rows and columns.

Data redundancy: Data redundancy means the repetition of data in a database.

Relational Database: A Database Management System that stores data in the form of related tables is known as a relational database.

Database model: A database model is the manner in which the data collection is stored, managed and administered.

Relationship: It is a link or association between several entries. Following is the list of different types of relationship

• One to one e.g: Driver and car
• One to many e.g: Teacher and students
• Many to many e.g: Books and readers
• Many to one e.g: Students and school

Primary key

A primary key is the field that uniquely identifies in a table. Each record in the table must be unique. Every table has only one primary key. There are two types of primary keys as follows.

• Compound (Composite key): A compound key is a key that consists of multiple columns because one column is not sufficient.
• Foreign key: A foreign key is the linking pin between two tables.

Data Type

A data type specifies the type of data that a field can hold. It is a form of storage which allows entry of previously defined values that each field can store. Some example of data types are as follows:

• Text Data Type
• Numeric Data Type
• Date Data Type

Objectives of Database

• Elimination of data redundancy.
• Share data among all users.
• Incorporate changes easily and quickly.
• Simplify the use of data files.
• Lower the cost of storing and retrieving data
• Improve accuracy and consistency.
• Provide data security from unauthorized access and use
• Exercise center control over standards.
• Get persist-ency in data.

Things to remember

• Database is a collection of data organized to service many applications at the same time by storing and managing data so they appear to be at one location.
• A database object comprising of related data entries is known as a table.
• A Database Management System that stores data in the form of related tables is known as a relational database.
• A database model is the manner in which the data collection is stored, managed and administered.

• It includes every relationship which established among the people.
• There can be more than one community in a society. Community smaller than society.
• It is a network of social relationships which cannot see or touched.
• common interests and common objectives are not necessary for society.

Questions and Answers

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