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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
|
