1. What is database?

A database is an organized collection of data that can be modified, retrieved, or update.

1. The data stored in the database, is in the row and column format, which is called a table.

2. Every website, which needs us to sign up, uses database.

3. Withouth database their is no internet.

2. Type of database

1. Object-Oriented databases (OODB):

This is database that represent data in the form of Object and Classes. In object-Oriented terminlogy, an Object is a real-world entity, ans class is a collection of objects. Example- PostgreSQL.

2. Realational Databases (RDBMS):

A database is a collection of data items with predefine relationship between them. These items are organized as a set of table with columns and rows. Example- MySQL.

3. Distributed databases (DDB):

A distributed database is integeted collection of databases that is physically distributed across sites in a computer network. Example- Cassandra.

4. Hierarchical databases:

A hierarchical database is a data model in which data is stored in the form of records and organized into a tree-like structure, in which one parent node can have many child nodes connected through links.Example- IBM information management system IMS

3. Database Management System-(DBMS)

1. Database management system is a software for storing and retrieving user's data while considering appropriate security measure.

2. It consist a group of programs which manipulate the database.

3. DBMS allows user's to create their own database as per their requirement. It provide an interface between data and the software application.

4. In large system a DBMS helps user's and others third-party software to store an retrieve data.

4. characteristics of DBMS

1. Real-World entity.

2. Realational Database.

3. Structure Query Languages.

4. ACID properties.

5. Transactional processing.

**1-Tier Architcture : ** This is simplest architecture of database in which client, server and database all resideon the same machine. Anytime you install a database in your system ans access it to practice SQL queries.But such architecture is rarely used in the production.

**2-Tier Architecture: ** This is database architecture where the presentation layer runs on a client (PC, Mobile, Tablet) and data is store on a server is called 2-tier architecture.

#3-Tier Architecture. This is very popular client server architecture in DBMS in which the development and maintenance os functional process, logic, data access, data storage and user interface is done independently as separate modules.

5. Database Schema

A database schema is the skeleton structure that represent the logical view of the enitire database. It define how the data organized and how the relation among them are associate. A database schema basically divided into two category.

1. Physical databse schema This schema pertains to the actual storage of the data and it's from storage like-file indices etc. It define how data store in secondary storage. 2. Logical databse schema This schema defines all the logical constrains that need to be applied on the data stored. It define- table, view and intigity constraints.

6. What is ER Model?

ER model stand for an Entity-Realationship model. It is a high-level data model. This model is used to define the data elements and relatonship for a specified system. It develop a conceptual design for the database.It also develops a very simple and easy to view of data. Search all points what are present in following diagram

7. Relational Database Management System- (RDBMS)

1. A realtional database is a type of database that store and provides access to data points that are related to one another.

2. Relational database are based on the relational model, an intutive, straightforward way of representing data in the from of table.

3. In a relational database, each row in the table is a record with a unique_ID called the key.

4. The columns of table hold attributes of the data.

5. The major DBMS like- SQL, MySQL, Oracle are all based on the principles of relation DBMS.

Advantages of RDBMS

1. Easy to manage, each table can be independently manipulated without affecting others.

2. Security- It is more secure consisting of multiple levels of security. Access of data shored can be limited.

3. User- RDBMS supports client-side architecture storing multiple user together.

8. SQL Basic command

If you want to use sql queries then you have to download and install a RDBMS. I 'm using MySQL.

1 following command is used for show your all existing databases. In my case you can see.

show databases;
 information_schema |
| mysql              |
| performance_schema |
| sakila             |
| sys                |
| world

2 How can we create a database? Here we are creating a school datatbase.

create database school;

3 How we can enter into our school database.

use school

4 How we can create a table. This is the example of a employee table.

create table employee(emp_id int, emp_name varchar(50), salary int, depart_id int, primary key(emp_id));

5 How to insert the data in employee datatbase

insert employee values(1, 'shivam', 100000, 1);

9. Learn MySQL