May 2024
Intermediate to advanced
325 pages
12h 2m
English
Content preview from Distributed Database Systems, 1st Edition by Chhanda Ray
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Distributed Database Systems
Create assertion salary_constraint check (not exists (select * from Employee where
salary < 20000)).
The above assertion imposes a restriction that salary should be greater than 20,000 and this condi-
tion must hold true in every database state for the assertion to be satisfi ed.
Example 12.6
The following is an example of a set-oriented assertion that involves two variables salary and
deptno and two relations Employee and Department.
Create assertion salarydept_constraint check (not exists (select * from Employee, Department
where salary < 20000 and Employee.deptno ⴝ Department.deptno)).
The above assertion also ...
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