The SQL stands for Structured Query
Language. It is a special purpose language used to manage data held in RDBMS
(Relational Database Management System). The capacity of SQL includes data
inserting, updating, deleting, query, schema creation and modification, and
controlling data access.
The SQL is an ANSI (American National
Standard Institute) standard. The SQL is used as a standard database language
by all the relational database systems like Oracle, MySQL, Microsoft SQL
Server, MS Access, Sybase, Informix and PostgreSQL.
History of SQL
Dr. E.F Codd proposed the relational model
for database system in 1970 and SQL was the first commercial language for this
relational model. This relational model also formed the basis for today’s
relational database management system (RDBMS).
The SQL was initially developed by IBM in
early 1970s. This version of SQL was called as SEQUEL (Structured English Query
Language). Later in 1970, the Relational Software, Inc (which is now Oracle
Corporation) developed their own SQL based RDBMS. The Oracle V2 for VAX
computers was the first commercially available implementation of SQL introduced
then by Relational Software, Inc.
Communication of SQL Statements with
RDBMS
The below diagram shows communication
of SQL commands with the RDBMS like oracle, MySQL, etc.
SQL Statement
The SQL statements are classified as shown
below.
Data Retrieval Language
|
Command
|
Description
|
|
select
|
used to retrieve records from
tables present in database
|
Data Manipulation Language (DML)
|
Command
|
Description
|
|
insert
|
used to insert record into database
|
|
update
|
used to update record present in
database
|
|
delete
|
used to delete records from
database
|
|
merge
|
used to merge two or more data
present in database
|
Data Definition Language (DDL)
|
Command
|
Description
|
|
create
|
used to create objects in database
|
|
alter
|
used to modify existing database
object
|
|
drop
|
delete entire objects from the database
|
|
rename
|
used to rename objects in database
|
|
truncate
|
used to remove a part of data or
round off the data present in database
|
Transaction Control
|
Command
|
Description
|
|
commit
|
used to save the changes made to
data in database
|
|
rollback
|
used to undo the transaction
performed
|
|
savepoint
|
used to set a savepoint within the
transaction
|
Data Control Language
|
Command
|
Description
|
|
grant
|
used to give any privilege to user
|
|
revoke
|
used to take by the privilege given
to the user
|
