Introduction to SQL

What is Relational Database?

Collection of Related Information in the form of Tables is Called Relational Database

There are so many databases are available in the market, some are free to use and some are licensed.

Example:

Oracle, DB2, Mysql, MS Access, Sql Server…and so…on.

 Let us take company Database where every company will have many departments such as HR, Sales, Production, and Finance and so…on, all these department data is stored into database.
Company Database
 

What is that Database has?

We should be familiar with the following fundamental database objects.

  1. What is Table?

  • Data in the database are stored in terms of table, it is a basic unit of storage in database.
  • It is contains rows and columns for storing the data.
  1. What is View?

  • It is a logical structure that contains data from tables virtually.
  • However these data are not stored physically in the database.
  1. What is Sequence?

  • Numeric values generator
  1. What is Index?

  • Improves the performance of some queries
  1. What is Synonym?

  • Gives alternative names to objects