Release 10.1A: OpenEdge Development:
Programming Interfaces

> ## Implementing other outer joins

> In addition to left outer joins, there are right and full outer joins. A right outer join reverses the join order for the same tables joined with a left outer join. In the 4GL, you can implement a right outer join by doing a left outer join with the tables in reverse order, but leaving the order of displayed fields the same as for the left outer join. Thus, the Unknown value (`?`) from the right side appear on the left side of each displayed row, as if the tables were joined from right to left.

> A full outer join combines the results of a left and right outer join into a single join. This is rarely used, but you can implement a full outer join by building one temporary table from the results of both a left and right outer join. For more information on temporary tables, see OpenEdge Development: Progress 4GL Handbook .

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