Temporal Join
This section presents actual Oracle source lines which
implement Temporal Joins as described in Chapter 3 of the TDB
book. This subsection, presents the following two approaches :
- Union-All - Uses Union-All to bypass the duplicate
elimination and sorting operations performed by the
ordinary Oracle UNION operator. Logically, sorting and
duplicate elimination should not be a by-product of a
join, so this approach seems more correct. However,
without elimination of duplicates, a special case were
there are tuples with exactly the same periods would need
to be considered. See the last select statement, and pay
close attention to the compound condition added to it.
-
- Union - This approach uses the basic UNION
operator, standard in SQL. This approach is more general,
but slower because it automatically eliminates duplicates
and sorts the results.
-
Note : All Source files, include code to
populate sample tables which would be coalesced. The result
files, contains the results of the experiment.
/jag