Mumbai University > Information Technology > Sem 5 > Advanced Database Management System

Marks: 5M

Year: Dec 2015

Difference between view & relational:-

View:-

1) This is one type of relation which is not part of physical database.

2) It has no direct or physical relation with database.

3) Views can be used to provide with securities mechanism.

4) Modification through a view (e.g. insert update delete) Not permitted

Base Relation:-

1) A base relation is a relation that’s not a derived relation.

2) While it can manipulate the conceptual or physical relations stored in data.

3) It doesn’t provide security.

4) Modification may be done with a base relation.

View:-

• We can assign the view a name & relate it query expression as

  Create view <view name=""> as <query expression="">

• View is a virtual table based on result-end of an SQL statement.
• View contains rows & columns, just like a real table. The fields in a view are fields from one or more real tables in database.
• You can add SQL functions, where, and join statements to a view & present data as it data were coming from one single table

Create view:-

Create view [current product list] as select product ID, product name from products

Where discontinued = No

We can create view, update view or replay and then drop view