:: - the target for a FK must be a constraint (an index won't do).
:: - when you define an unique constraint, an unique index is
:: implicitly created.

If I create a constraint, will the index it creates be used for searches and
sorting? So again.. Now I am REALLY confused.. Whas the difference between a
unique constraint and a unique index? I know Helen replied - and it made a
little sense but now Im more confused than before.

:: - when you define an unique index, you have practically the
:: same effect as defining an unique constraint, minus the
:: ability to have FKs point to it.

Why though? And what difference in them causes this?