On Tue, Jun 20, 2006 at 00:49:21 -0400,
louis gonzales <gonzales@linuxlouis.net> wrote:
> Florian,
> I understand where you're coming from. Indexes are always unique and
> all RDBMS systems use them to 'uniquely' identify a row from the the
> perspective of internal software management. Index != PrimaryKey, so
> every table created, despite any Primary/Foreign key contraints put on
> them, always have a 1-1 Index per row entry. At least that's the way I
> understand it, can someone else affirm this statement or redirect a
> misguided 'me ;)'?
Note that indexes are not always unique. They can sometimes still be useful for
speeding up performance even when there are duplicates. Postgres also has
partial indexes which cover only some of the rows in a table, based on
a where condition.