
Distributed Query Processing
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query. The well-known idempotency rules of Boolean algebra are used to eliminate redundancies
from the given query, which are listed below.
P ∧ P ⇔ P
P ∨ P ⇔ P
P ∧ true ⇔ P
P ∧ false ⇔ false
P ∨ true ⇔ true
P ∨ false ⇔ P
P ∧ (∼P) ⇔ false
P ∨(∼P) ⇔ true
P ∧ (P ∨ Q) ⇔ P
P ∨ (P ∧ Q) ⇔ P
Example 11.6
Let us consider the following view defi nition and a query on the view that involves the relation
Employee (empid, ename, salary, designation, deptno).
Create view V1 as select empid, ename, salary from Employee where deptno ⴝ 10;
Select * from V1 where deptno ⴝ 10 and salary > 10000;
During query resolution, the query will be:
Select ...