What is data?
The Latin word Data is a plural form of datam. Datam means an item of information. Over the course of time data is now commonly used in singular form. Data is the smallest part of information. It can be any character, number, symbol, picture, video, sound or any object.
Every organization has some information needs. A library, for example, keeps a list of members, books, due dates and fines. A company needs to save information about employees, departments, and salaries. These pieces of information are called data. These data is just data until it is organized in a meaningful way, at which point it becomes information. So, a large volume of data needs to be processed to generate information. In other words, information is organized and meaningful outcome of data processing.
What is database?
A database is an organized collection of related data serving a central purpose. It is organized in the sense that it contains data that is stored, formatted, accessed, and represented in a consistent manner. It serves a central purpose in that it does not contain extraneous or superfluous data.
A phone book is a good example of database. It contains relevant data ‘names’ that enable access to phone numbers.
There are huge similar databases like business databases, scientific databases, military databases, educational databases, and the list goes on and on.
Modern databases contain many types of data other than text and numeric. It is now common to find databases storing pictures, graphs, audio, video, or documents etc. With the advent of Internet technology databases now serve as back ends for Web browser front ends.
Elements of Database:
Table : Table is a database structure. Sometimes it is called datasheet. A relational table has a set of named attributes or columns, and a set of tuples, or rows. Sometimes a column is referred to as a field. Sometimes a row is referred to as a record. A row and column intersection is usually referred to as a cell. A relational table must meet some special criteria to be a part of the relational modal:
- Data stored in cells must be atomic. Each cell can hold one piece of data only.
- Data stored in a columns must be of the same data type.
- Each row is unique. No duplicate rows are allowed.
- Columns have no order to them.
- Columns have a unique name.
Record: A record is a group of data of some related field held within the same data structure. For example, for a student of an institution entity, the field would be roll, name, address, mobile no, etc. to make a record.
Field: Field is a column of a table that stores data of the same category with same data type. Each Field has a unique name. It is a column heading in a table. In an employee table, the field would be the employee number, name, job, title, department number and so on. Each field contains values of certain length.
Entity: A thing of significance about which information needs to be known is called entity. A table is identified by an entity. The entity may have a real existence or not. Examples are departments, employees, and orders.
Attribute: Something that describes or qualifies an entity. It is another name of a field in a table.
Types of Database:
There are four main types of Database.
Hierarchical Database: A hierarchical database is a database where the data are organized into a tree-like structure. It represents a parent-child relationship where a single parent has many children. This database model was developed by IBM in the 1960s.
Network Database: The network database is a database model where a child can be linked to multiple parents (Here the children are members and the parents are owners). That means this model allows each record to have multiple parent and multiple child records.
Relational Database: A relational database is a type of database that uses relations or two-dimensional tables to store information. This model is used widely around the world for data storage and processing. Relational database model requires two fundamental integrity rules. These are the entity integrity rule and the referential integrity rule.
Object-relational Database: The object-relational database model is the combination of relational database model and object-oriented database model. Like Object-Oriented models it supports objects, classes, inheritance etc. and like Relational data model it has support for data types, tabular structures etc