sys_op_map_nonnull

The best translation for the value NULL in SQL I can work with is unknown. Therefor, the test if null = null then is false, because we cannot know if the unknown thing on the left side of the = is the same unknown thing on the right side.

However, sometimes, it seems reasonable that null = null should indeed be true. In such a case, sys_op_map_nonnull can be used.

Warning: sys_op_map_nonnull is undocumented and there is no guarantee that it is always working as described here.

select a, b, c from t where
sys_op_map_nonnull(f) = sys_op_map_nonnull(g);