Messages In This Digest (2 Messages)

1a.: Come on guys.................. From: sn_k000
1b.: Re: Come on guys.................. From: Mat Gemboel

View All Topics | Create New Topic

Messages

1a.: Come on guys..................

Posted by: "sn_k000" sn_k000@yahoo.com sn_k000

Fri Oct 21, 2011 3:36 am (PDT)

http://www.ezyoracle.com

What is a View?
You can persent logical subsets or combinations of data by creating views of tables. A view is a logical table based on a table or another view. A view contains no data of its own but is like a window through which data from tables can be viewed or changed. The tables on which a view is based are called base tables. The view is stored as a SELECT statement in the data dictionary.

Advantages of Views
Views restrict access to the data because the view can display selective columns from the table.
Views can be used to make simple queries to retrieve the results of complicated queries. For example, views can be used to query information from multiple tables without the user knowing how to write a join statement.
Views provide data independence for ad hoc users and application programs. One view can be used to retrieve data from several tables.
Views provide groups of users access to data according to their particular criteria.

http://www.ezyoracle.com

Here is used create view format in practice :

SQL> CREATE OR REPLACE VIEW salvu50
As SELECT employee_id, last_name, salary, department_id
FROM employees
WHERE department_id = 50;
View created.

Creating a View

You can create a view by embedding a subquery within the CREATE VIEW statement.

OR REPLACE re-creates the view if it already exists.
view is the name of the view.
alias specifies names for the expressions selected by the views query (The number of aliases must match the number of expressions selected by the view).
subquery is a complete SELECT statement (You can use aliases for the columns in the SELECT list.).
WITH CHECK OPTION specifies that only rows accessible to the view can be inserted or updated
constraint is the name assigned to the CHECK OPTION constraint
WITH READ ONLY ensures that no DML operations can be performed on this view

http://www.ezyoracle.com
Retrieving Data from a View

SELECT *
FROM salvu50;

http://www.ezyoracle.com

Back to top
Reply to sender | Reply to group | Reply via web post
Messages in this topic (2)
1b.: Re: Come on guys..................

Posted by: "Mat Gemboel" si_mat_gemboel@yahoo.com.sg si_mat_gemboel

Fri Oct 21, 2011 3:54 am (PDT)

Rekan sn_k000,

Iklan neh ?
*asahgolog*
_____________
Best regards,
Mat Gemboel
si_mat_gemboel@yahoo.com.sg

Friday, October 21, 2011, 2:15:16 PM, sn_k000 [sn_k000@yahoo.com] wrote:
> What is a View?

Back to top
Reply to sender | Reply to group | Reply via web post
Messages in this topic (2)