Hi, Today i will discuss about important topic - VIEW.
In Oracle, view is a virtual table that does not physically exist. It is stored in Oracle data dictionary and do not store any data. It can be executed when called.
A view is created by a query joining one or more tables.
CREATE VIEW
To create view , we follow same query as create table. see the syntax.
Syntax:
CREATE VIEW view_name AS
SELECT columns
FROM tables
WHERE conditions;
Example:
CREATE VIEW student_from_delhi AS
SELECT * FROM students
WHERE student_city = 'Delhi';
View created.
To see created View:
SELECT * FROM student_from_delhi;
UPDATE VIEW:
Syntax:
CREATE OR REPLACE VIEW view_name AS
SELECT columns
FROM table
WHERE conditions;
Example:
CREATE or REPLACE VIEW student_from_delhi AS
SELECT * FROM students
WHERE student_city = 'Delhi' AND student_type='Day Scholar' ;
DROP VIEW:
The DROP VIEW statement is used to remove or delete the VIEW completely.
Syntax:
DROP VIEW view_name;
Example:
DROP VIEW student_from_delhi;
View dropped.
If you want to see VIEW "student_from_delhi" after DROP, It will give following output:
ORA-00942: table or view does not exist
Thank you for reading. Feel Free to ask you Query in comment section.