Bài giảng Cơ sở dữ liệu - Chương 9, Phần 3: View - Nguyễn Hồng Phương
10/11/2019
Contents
Introduction
Creating a view
View
A view from two tables
Dropping a view
Updating a table from a view
NGUYEN HongPhuong
Email: [email protected]
Hanoi University of Science and Technology
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Introduction
Creating a view
In SQL, a view is a virtual table based
Syntax
on the result-set of an SQL statement.
CREATE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
A view contains rows and columns, just
like a real table. The fields in a view are
fields from one or more real tables in
the database.
WHERE condition;
You can add SQL functions, WHERE,
and JOIN statements to a view and
present the data as if the data were
coming from one single table.
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Creating a view
Querying on a view
Examples
CREATE VIEW vCompany1 AS
SELECT Name, Address, Telephone
FROM Company
SELECT * FROM vCompany1
WHERE Address LIKE'%Germany%';
CREATE VIEW vCompany2 AS
SELECT Name, Address, Telephone
FROM Company
SELECT * FROM vCompany2;
WHERE Address LIKE '%Japan%'
CREATE VIEW vComSupPro1(ComName, ProdName, Qty) AS
SELECT Company.Name, Product.Name, Quantity
FROM Company INNER JOIN Supply ON Company.CompanyID
= Supply.CompanyID
INNER JOIN Product ON Supply.ProductID = Product.ProductID
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Deleting a view
Syntax
DROP VIEW view_name;
Example
DROP VIEW vCompany1;
DROP VIEW vCompany2;
DROP VIEW vComSupPro1;
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