Introduction to Database


Data

A fact in real world is known as data. Ex- name, date of birth, phone number, email id etc.

Information

Processed data is known as information. Ex- People whose birthday is in this month.

Database

Database is a permanent memory where we are storing data in the manner so that search, insert, update, and delete operations become easy.

DBMS

DBMS stands for database management system. It is a kind of software which is responsible for defining the storage structure and also provides some processes for managing the data.

RDBMS

RDBMS stands for relational database management system.

It is based on relational model where Data is stored in the form of rows and columns, known as database table and tables can be linked together.



SQL command
1. Data Query Language
SELECT : is used to get the data from tables.
2. Data Definition Language

Data Definition Language (DDL) commands are used to define the database object or schema. DDL commands are auto commit.

CREATE    : is used to create new database objects.
ALTER     : is used to modify existing database objects.
DROP      : is used to remove database objects permanently.
TRUNCATE  : is used to remove all the rows permanently from a table
RENAME    : is used to change name of an database object
3. Data Manipulation Language

Data Manipulation Language (DML) commands are used for managing data (insertion, updation, deletion etc) within database objects. DML commands are not auto commit.

INSERT : is used to add new rows into a table.
UPDATE : is used to modify existing rows in a table.
DELETE : is used to remove rows from a table.
4. Transaction Control Language

Transaction Control (TCL) statements are used to manage the changes made by DML commands.

COMMIT   : is used to save changes made in a transaction
ROLLBACK : is used to revert back the changes made in a transaction
SAVEPOINT: is used to divide a transaction
5. Data control Language

Data control Language (DCL) statements are used to provide or deny access of database object.

GRANT  : is used to provide access to database object.
REVOKE : is used to deny access from user.
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