What is DBMS

What is DBMS?

DBMS is the abbreviated form of DataBase Management System.

Database management system is a computer software component introduced during 1960’s. It is used for controlling various databases in the desktop computer or server. It was also termed as Navigational Database Management System. During 1970’s RDBMS or Relational database management system came into existence. We’ll see about RDBMS later in this article.

Database management system is the means of controlling databases either in the hard disk in a desktop system or on a network. Database management system is used for creating database, maintained database and provides the means of using the database. DBMS doesn’t consider relationship between the tables. Instead it will take the approach of manual navigation. This has led to severe performance problems when dealing with complex and high amount of data.

DBMS has several components. Some of the major components are external interface, database language engine, query optimizer, database engine, storage engine, DBMS management component, etc..

External Interface

External Interface is the user interface which is used to communicate with the DBMS as well as the databases.

Database language engine

Database language engine is the one which interprets the query language and do the necessary action supplied using the query language.

Query Optimizer

Query optimizer is used to optimize the supplied query language and identifies the best plan for executing the query and obtaining the result as fast as it could.

Database Engine

Database engine is used to create or manipulate the data in the database objects like table.

DBMS Management Component

DBMS Management Component comprises of several other components. They are used to take database backups, performance monitoring, security management etc.

Types of DBMS

There are several database management system models. Some of them are Navigational, RDBMS, SQL DBMS and� object-oriented databases. You can read more about the types of DBMS in my other article (Types of DBMS).

What is RDBMS?

RDBMS is the abbreviated form of Relational DataBase Management System.

Relational database management system was introduced in 1970’s. RDBMS avoided the navigation model as in old DBMS and introduced Relational model. The relational model has relationship between tables using primary keys, foreign keys and indexes. Thus the fetching and storing of data become faster than the old Navigational model. So RDBMS is widely used by the enterprises and developers for storing complex and large amount of data.

RDBMS table relationship diagram

Database Management System vs. Relational Database Management System:

The below table lists downs some of the major differences between DBMS and RDBMS.

Sl.#	DBMS	RDBMS
1	Introduced in 1960s.	Introduced in 1970s.
2	During introduction it followed the navigational modes (Navigational DBMS) for data storage and fetching.	This model uses relationship between tables using primary keys, foreign keys and indexes.
3	Data fetching is slower for complex and large amount of data.	Comparatively faster because of its relational model.
4	Used for applications using small amount of data.	Used for complex and large amount of data.
5	Data Redundancy is common in this model	Keys and indexes are used in the tables to avoid redundancy.
6	Example systems are dBase, Microsoft Acces, LibreOffice Base, FoxPro.	Example systems are SQL Server, Oracle , MySQL, MariaDB, SQLite.

Functions of DBMS

·         Provides data Independence

·         Concurrency Control

·         Provides Recovery services

·         Provides Utility services

·         Provides a clear and logical view of the process that manipulates data.

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Advantages of DBMS

·         Segregation of applicaion program.

·         Minimal data duplicacy.

·         Easy retrieval of data.

·         Reduced development time and maintainance need.

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Disadvantages of DBMS

·         Complexity

·         Costly

·         Large in size

Normalization of Database

Database Normalisation is a technique of organizing the data in the database. Normalization is a systematic approach of decomposing tables to eliminate data redundancy and undesirable characteristics like Insertion, Update and Deletion Anamolies. It is a multi-step process that puts data into tabular form by removing duplicated data from the relation tables.

Normalization is used for mainly two purpose,

·         Eliminating reduntant(useless) data.

·         Ensuring data dependencies make sense i.e data is logically stored.

Normalization Rule

Normalization rule are divided into following normal form.

1.    First Normal Form

2.    Second Normal Form

3.    Third Normal Form

4.    BCNF

Boyce and Codd Normal Form (BCNF)

Symbols and Notations

Overview of SQL queries SQL tutorial gives unique learning on Structured Query Language and it helps to make practice on SQL commands which provides immediate results. SQL is a language of database, it includes database creation, deletion, fetching rows and modifying rows etc.

SQL is an ANSI (American National Standards Institute) standard but there are many different versions of the SQL language.

What is SQL?

SQL is Structured Query Language, which is a computer language for storing, manipulating and retrieving data stored in relational database.

SQL is the standard language for Relation Database System. All relational database management systems like MySQL, MS Access, Oracle, Sybase, Informix, postgres and SQL Server use SQL as standard database language.

Also, they are using different dialects, such as:

·        MS SQL Server using T-SQL,

·        Oracle using PL/SQL,

·        MS Access version of SQL is called JET SQL (native format) etc.

Why SQL?

·        Allows users to access data in relational database management systems.

·        Allows users to describe the data.

·        Allows users to define the data in database and manipulate that data.

·        Allows to embed within other languages using SQL modules, libraries & pre-compilers.

·        Allows users to create and drop databases and tables.

·        Allows users to create view, stored procedure, functions in a database.

·        Allows users to set permissions on tables, procedures, and views

History:

·        1970 -- Dr. Edgar F. "Ted" Codd of IBM is known as the father of relational databases. He described a relational model for databases.

·        1974 -- Structured Query Language appeared.

·        1978 -- IBM worked to develop Codd's ideas and released a product named System/R.

·        1986 -- IBM developed the first prototype of relational database and standardized by ANSI. The first relational database was released by Relational Software and its later becoming Oracle.

SQL Process:

When you are executing an SQL command for any RDBMS, the system determines the best way to carry out your request and SQL engine figures out how to interpret the task.

There are various components included in the process. These components are Query Dispatcher, Optimization Engines, Classic Query Engine and SQL Query Engine, etc. Classic query engine handles all non-SQL queries but SQL query engine won't handle logical files.

SQL Commands:

The standard SQL commands to interact with relational databases are CREATE, SELECT, INSERT, UPDATE, DELETE and DROP. These commands can be classified into groups based on their nature:

DDL - Data Definition Language:

Command	Description
CREATE	Creates a new table, a view of a table, or other object in database
ALTER	Modifies an existing database object, such as a table.
DROP	Deletes an entire table, a view of a table or other object in the database.

DML - Data Manipulation Language:

Command	Description
SELECT	Retrieves certain records from one or more tables
INSERT	Creates a record
UPDATE	Modifies records
DELETE	Deletes records

DCL - Data Control Language:

Command	Description
GRANT	Gives a privilege to user
REVOKE	Takes back privileges granted from user