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.
|
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.
Advantages of DBMS
·
Segregation of applicaion program.
·
Minimal data duplicacy.
·
Easy retrieval of data.
·
Reduced development time and maintainance need.
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
|
