SQL overview

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This is my new blog for SQL beginners. My motto is to guide you to learn SQL from basic steps. Here you find all the basic concepts of SQL language.

As am working professional in this field, I’ll give you the basics knowledge of SQL in this blog.

All you need to do is just follow this blog. Today am posting about overview of SQL and some basic concepts. Here we go…

SQL Overview:

What is SQL?

 'SQL' stands for Structural Query Language. SQL is language used to communicate or interact with database. It is use for creating new database, table. By using SQL we can insert, update or delete record in database. It is standard language for relational database system.

What is Database?

Database is storage or collection of organized information. It is structured set of information which is easy to retrieved, maintained and update. Basically database is made up of objects like tables, stored procedures etc. Data is stored in form of rows and columns in table.

What is RDBMS ?

RDBMS is a Relational Database Management System. Relational Database is most used database. It contains table which contains one primary key and have relation to multiple tables.

Advantages of RDBMS  :-

•  Simple structure, easy to access and use.
•  Allow administrator to grant access or privilege to specific user.
•  Allow multiple users to access database simultaneously.
•  Locking and prevent collision or interference of activities between two users.
•  Provides tool to database administrator for easy maintenance, repair and back up.

What is Table?

Table is collection of related data in form of rows and columns stored in database object.

For ex. Following tables shows data for employees of company.

EMPLOYEE TABLE

What is Field?

Field is single piece of data in table. It is subject of data in record.

Fields are appears as columns in table.

All Data in single column is of single data type.

For Ex.  

What is Record?

Record is collection of data contains fields. Fields may be single or multiple.

Record is also called as Row in table.

For Ex.    

What is Data Type?

SQL data type is an attribute that specifies the type of any object. It shows what type of data is allowed to store in particular object.

Followings are the most commonly used data types in SQL:

Data type	Description
Character	Character string. It have fix length
Varchar	Character string having variable length
Number	Numeric value
Binary	Binary string
Boolean	Stores value TRUE or FALSE
Integer	Integer numerical value with no decimal
Float	Approximate numerical
Date	Stores year, month, and day values
Time	Stores hour, minute, and second values
Timestamp	Stores year, month, day, hour, minute, and second values