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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
Explain Candidate Key and Super Key A super key is a set of one or more than attributes that, taken collectively, permits us to identify uniquely a tuple in the relation. Wher
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Describe briefly models which define the operations on classes. The three models which are used to define operations on classes are as: Object Model = data dictionary + Obje
Improved availability: The data in a distributed system may be replicated so that it is at more than one site. Thus, the failure of a node or a communication link does not necessar
how to implement hyrise in C plus plus
Consider employee table of (i) and list names of department(s) for which average salary for department is more than 10,000. (SELECT d_name FROM dept WHERE d_code IN (SELECT d_c
Describe about Use Case and external case in DFD The processes are transformed those into the Use Case and external case in DFD has same characteristics which of an actor in O
non numeric literals
Modify a sequence: ALTER SEQUENCE SEQSS INCREMENT 2 MAXVALUE 3000; Removing a sequence: DROP SEQUENCE SEQSS;
A relation instance indicates as r is a collection of tuples for a given relational schema at a exact point of time. A relation state r of the relation schema R (A 1 ,A 2 ,.....
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