SQL
stands for Structured Query Language which is used against RDBMS to manage data.
SQL
commands have been divided in many categories but frequently used commands are:
1- DDL (Data Definition Language)
2- DML (Data Manipulation Language )
3- DRL (Data Retrieval Language )
3- DRL (Data Retrieval Language )
4- TCL (Transaction Control Language)
5- DCL (Data Control Language)
DDL (Data Definition Language) Statements are used to define the
database object structure. DDL commands are auto- committed.
·
CREATE - Used to create Objects in
Database i.e Table, Views, Triggers etc.
·
ALTER – Used to modify Object Structure
in Database.
·
DROP – Used to Delete Objects from
Database.
·
TRUNCATE – Removes all records from a
Table.
DML (Data Manipulation Language) Statements are used to Store, Modify, Delete
data in database. DML commands are not auto-committed.
· INSERT –Used to insert data into a table, "INTO" KEYWORD is not necessary in the query. You can insert default values using this insert statement : INSERT TABLENAME DEFAULT VALUES().
·
UPDATE – Used to updates existing data
within a table
·
DELETE – Used to deletes records from a
table
·
MERGE – Used for insert-update
operation.
DRL (Data Retrieval Language) Statements are used to Retrieve data from the database.
· SELECT – Used to retrieve data from the a database
DRL (Data Retrieval Language) Statements are used to Retrieve data from the database.
· SELECT – Used to retrieve data from the a database
TCL (Transaction Control Language) these commands are used to manage transaction in
database. These are used to manage changes made by DML.
·
COMMIT – Permanently save work in
database.
·
SAVEPOINT – This command identify a point
in a transaction so that you can roll back later if required.
·
ROLLBACK – This command restores database
to original since the last COMMIT
DCL (Data Control Language) these commands are used to manage privilege in
database.
·
GRANT – This command gives user access
privileges to database
·
REVOKE – This command withdraw access
privileges given with the GRANT command
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