CBSE Class 11 Informatics Practices Introduction to SQL

Introduction to MySQL

These days computerized databases can be seen being used almost everywhere. The police force uses various computerized databases to help them track criminals and solve crimes. A library stores details of all their books, in a computerized database. When we want to know if a book is in stock, we cannot only look it up, but can also check when it is due to be returned.

The database also records details of all the borrowers, what books they currently have borrowed and when they are due back.

What is Database Management System(DBMS)?

To create and maintain a database on a computer, we need a database program, called a Database management system, or DBMS. Database Management System is a software that enables users to create and maintain databases. Examples of popular DBMSs are MySQL, PostgreSQL, Microsoft Access, Oracle, Microsoft SQL Server, DB2 and Sybase.

A DBMS gives us tools to:

Store data in a structured way.

Query the database (that is, ask questions about the data)

Sort and manipulate the data in the database

Validate the data entered and check for inconsistencies

Produce flexible reports, both on screen and on paper, that make it easy to Comprehend the information stored in the database.

Tables in a Database

Relational Databases store data or information in tables. A table is similar to a spreadsheet where data is stored in rows and columns. A table refers to a two dimensional representation of data using rows and columns. 

 The horizontal subset of the Table is known as a Row/Tuple. Each row represents a record, which is a collection of data about a particular person, place or thing. The vertical subset of the Table is known as a Column/Attribute. The term field is also often used for column. Each column has a unique name and the content within it must be of the same type.

 Relational Database

In the database named Learner shown below, the data is organized into separate tables. Once the tables have been set up, a relationship can be created to link them together. Such a database that stores data in separate tables that are related through the use of a common column is called a Relational database.

RDBMS Terminology: Admission_No RollNo Name Class Sec Dues

Primary key

When you got admission in the school, you were given an Admission number. The Admission number assigned to you was not assigned to any other student of your school (it is unique). When patients go to a hospital, each patient is given a unique patient number. When you go to open an account in the bank, you are given a unique account number. Admission number, Patient number, Account number are all examples of Primary key. A primary key is a field in a table that is unique for each record. Every database table should have a column or a group of columns designated as the primary key. The value this key holds should be unique for each record in the table. Some more examples of Primary key are: Accession Number of a Book in the Book table, Employee ID of an employee in the Employee Table, Item Code of an item in the Stock table, Flight Number of a flight in the Flight Master Table, etc.

Please refer to the link below - CBSE Class 11 Informatics Practices Introduction to SQL