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Creating views with check option: This option limits those updates of data values that cause records to go off the view. The following instance tells this in more detail:
Example: To produce a view for employees of Department = 30, such that user cannot alter the department number from the view:
CREATE OR REPLACE VIEW EMPD30 AS
SELECT EMPNO EMPL_NUM, ENAME NAME, SAL SALARY FROM EMP
WHERE DEPTNO=30
WITH CHECK OPTION;
Now the user cannot alter the department number of any record of view EMPD30. If this change is permitted then the record in which the change has been made will go off the view as the view is only for department-30. This restricted due to use of WITH CHECK OPTION clause
What is the used of specifying alias? Specifying alias: is used to rename column or attribute in a table.
Timestamps For Read operations: If TS (T) If TS (T) >= W-timestamp (Q), then the transaction T is trying to read a value of data item Q which has been written and committed
What is magnetic disks?explain it? Magnetic disk provides the bulk of secondary storage of modern computer system. The disk capacity is growing at over 50% per year. But the st
When are two schedules said to be view equivalent? Ans: Two schedules that is denoted as S and S' are said to be view equivalent if the subsequent three conditions are met
What is the difference between a key and a superkey? Key - A key a single attribute or a combination of two or more attributes of an entity set which is used to identify one
Design Of Distributed Databases: The distributed databases are mainly relational at local level. So a local database schema is the similar as that of a centralised database design
The entity type STUDENT has the following attributes: Student Name, Address, Phone, Age, Activity, and No of Years. Activity represents some campus-based student activity, and No o
CAN SOMEONE HELP ME WITH ENTITY DIAGRAMS IN FIRST NORMAL FORM?
What are the drawbacks of File Oriented System in details?
Command Line Interfaces: These are interactive interfaces, character-based that let you use the complete power and functionality of the DBMS query language directly. They permit yo
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