Basics of Database

Database:

• A database is an organized collection of data.
• Database is the collection of schemas, tables, queries, reports, views and other objects.
• In one view, databases can be classified according to types of content: bibliographic, full-text, numeric, and images.
• A database is a collection of Tables, Schemas, Buffer pools, Logs, Storage groups and Table spaces working together to handle database operations efficiently.
• To access information from a database, you need a DBMS. This is a collection of programs that enables you to enter, organize, and select data in a database.
• You can create a database in instance using the “CREATE DATABASE” command.

DataBase Management System(DBMS):

• A database management system (DBMS) is a computer software application that interacts with the user, other applications, and the database itself to capture and analyze data. 
• A database management system (DBMS) is a collection of programs that manages the database structure and controls access to the data stored in the database.
• DBMSs include MySQL, PostgreSQL,Microsoft SQL Server, Oracle, Sybase and IBM DB2.
• Sometimes a DBMS is loosely referred to as a database.
• The DBMS serves as the intermediary between the user and the database. 

Relational DataBase Management System(RDBMS):

• RDBMS is the basis for SQL, and for all modern database systems like MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access. 
• It is based on the relational model as invented by E.F.Codd.
• Relational databases have often replaced legacy hierarchical databases and network databases because they are easier to understand and use

Levels of Database:

• The external level defines how each group of end-users sees the organization of data in the database. A single database can have any number of views at the external level.
• The conceptual level unifies the various external views into a compatible global view.It provides the synthesis of all the external views.
• The internal level or physical level is the internal organization of data inside a DBMS. It is concerned with cost, performance, scalability and other operational matters.

Languages:

• Data definition language – defines data types and the relationships among them
• Data manipulation language – performs tasks such as inserting, updating, or deleting data occurrences
• Query language – allows searching for information and computing derived information

Applications:

• Support internal operations of organizations.
• It is used to hold more specialized information.

Examples:

• Computerized Library System
• Telephone directories
• Online Reservation System
• School registers

Advantages:

• Improved data sharing.
• Integrity can be enforced
• Minimized data inconsistency.
• Providing Backup and Recovery
• Improved data security.
• Concurrency Control 
• Data Atomicity
• Controlling Redundancy
• Cost of developing and maintaining system is lower
• Data Independence
• Support Transactions
• Improved decision making

Disadvantages:

• Cost of Staff Training is high
• Cost of Hardware and Software
• Damage occur in Database 
• It is only efficient for particularly large organizations.
• Occupy more size
• Database systems are complex (due to data independence), difficult, and time-consuming to design.