is simple. If the relation R with its attribute A is joined with the relation S with its attribute B via an
equijoin operation, where A is a key of the relation R, and B is a foreign key of relation S, then the
cardinality of the join operation can be evaluated as follows.
card(R
Ԯ
A ⴝ B
S) ⴝ card (S).
In the above evaluation, it is assumed that the each tuple of relation R participates in the join opera-
tion; therefore, the above estimation is an upper bound. In other cases, it can be calculated as
card(R
Ԯ
S) ⴝ SF
J
* card(R) * card(S)
5.Semijoin Operation
The selectivity factor of the semijoin operation of the ...
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