Question

Which of the following is an advantage of view in databases? 
1. Data security
2. Hiding of complex queries
3. Derived columns
4. All of the above

Answer 1

Correct Answer - Option 4 : All of the above

The Correct Answer is "All of the above".

Advantages of views :

• Security
  • Each user can be given permission to access the database only through a small set of views that contain the specific data the user is authorized to see, thus restricting the user's access to stored data.
• Query Simplicity
  • A view can draw data from several different tables and present it as a single table, turning multi-table queries into single-table queries against the view.
• Structural simplicity
  • Views can give a user a "personalized" view of the database structure, presenting the database as a set of virtual tables that make sense for that user.
• Consistency
  • A view can present a consistent, unchanged image of the structure of the database, even if the underlying source tables are split, restructured, or renamed.
• Data Integrity
  • If data is accessed and entered through a view, the DBMS can automatically check the data to ensure that it meets the specified integrity constraints.
• Logical data independence.
  •  The view can make the application and database tables to a certain extent independent. If there is no view, the application must be based on a table. With the view, the program can be established in view of above, to view the program with a database table to be separated.

• Disadvantages of views :
• Performance
  • Views create the appearance of a table, but the DBMS must still translate queries against the view into queries against the underlying source tables. If the view is defined by a complex, multi-table query then simple queries on the views may take considerable time.
• Update restrictions
  • When a user tries to update rows of a view, the DBMS must translate the request into an update on rows of the underlying source tables. This is possible for simple views, but more complex views are often restricted to read-only.

• View is the simple subset of the table which is stored logically in a database means a view is a virtual table in the database whose contents are defined by a query. 
• To the database user, the view appears just like a real table, with a set of named columns and rows of data. SQL creates the illusion of the view by giving the view a name as a table name and storing the definition of the view in the database.