Netsteps Knowledge Base

When joining left, all tuples of original relation should be shown, even when JOIN Condition results to NULL:
eg:
SELECT * FROM original
LEFT JOIN detail USING (id_join)

When restricting tuples using a contition on detail, eg
SELECT * FROM original
LEFT JOIN detail USING (id_join)
WHERE id_detail IN(1,2,3)
Some Tuples of original may be supressed.

This is due to the fact, that the result of the JOIN ist filtered.