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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 a virtual table that draws its data from the result of an SQL SELECT statement? View is a virtual table that draws its data from the result of an SQL SELECT statement.
What is a transaction ? The Transaction is a unit of data processing. For instance, many of the transactions at a bank may be withdrawal or deposit of money; transfer of money f
What is D command work in the respect of QBE? D: It is the command inside QBE to delete tuple(s) from the relation.
By using the delete operation some consisting records can be deleted from a relation. To delete some definite records from the database a condition is also specified based on which
Explain the Dynamic Hashing Techniques There are two methods in it: extendible hashing - stores an access structure in addition to the file, and therefore is somewhat identica
Lost Updates : Suppose the two transactions T3 and T4 run simultaneously and they happen to be interleaved in the following way (suppose the initial value of X as 10000):
Scenario: You are a freelance database designer who has just been contacted by a small software development company named Altair Software. The president of the company has asked
multidimensional data model
Depending upon the rules we have found, we can classify the locks into two types. Shared Lock: A transaction might be acquiring shared lock on a data item in order to read it
What is a security? Securities are claims on financial assets. They can be illustrated as "claim checks" which give their owners the right to receive funds in the future. Sec
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