# 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 :

1. 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.
2. - Oracle SQLPLUS code (Tjoin.SQL)
   - Result (TJoin.result)
3. 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.
4. - Oracle SQLPLUS code (Tjoin.SQL)
   - Result (TJoin.result)

Note : All Source files, include code to populate sample tables which would be coalesced. The result files, contains the results of the experiment.

/jag