Learn SQL :What is SQL Database , What is SQL Tables , And How it is Implemented.

Let's start with the basic things of SQL:

What is Database?

• A database is the organised collection of the data or we can say a database is a container that hold tables and other SQL structures related to those tables.

• The main purpose of creating the database is to operate large amount of information by storing, retrieving and managing.

• A database is generally represented by a cylindrical structure.

   

What are tables?

 

A table is the structure inside the database that contains data, organized in 'columns' and 'rows'

Roll no.	Name	Mobile no.
1	Aashu	81765
2	Ajeet	83567
3	Aakriti	74653

Fields : It is a small entity of the table which contain specific information about each records or  row of the table.

In above table fields are  "Roll no., Name, Mobile no."

Records or Row : It is the horizontal entity which contain specific information about each individual entry.  

Example:

1

Aashu

81765

Columns :  It is the vertical entity which contain specific information associated with the fields.

Example:
               Aashu
               Ajeet
               Aakriti

SQL Syntax:

1. SQL is not case sensitive means we can use upper and lower 
    case both. But generally the keywords or commands are written      in upper case letter

2. We can write SQL statement on one or multiple lines.

 
SQL commands:

• Some of the SQL commands are:

Command	How they work
SELECT	It extracts data from a database.
UPDATE	It updates data in database.
DELETE	It deletes data from database.
CREATE TABLE	It is used to create the table.
DROP TABLE	It deletes a table.
ALTER TABLE	It is used to modify a table.
CREATE DATABASE	It creates a new database.
ALTER DATABASE	It is used to modify a database.
INSERT INTO	It inserts new data into a database.

SOL Datatypes:

Some common datatypes are:

DATATYPE	SYNTAX	EXPLANATION
Integer	INT	It is used to specify an integer.
Character	CHAR(x)	Here 'x' is  the character's number to store.
Decimal	DEC(x,y)	It specify a decimal value in which 'x' is precision value and 'y' is scale value.
	VARCHAR()	It holds text data both in characters and numbers.
Blob	BLOB	It is same as CHAR or VARCHAR except the range of storing the text. It can hold more than 256 character.
Date	DATETIME	It is used to store future event.
Date	TIMESTAMP	It is used to capture the current date

Previous                                                                                      Next