Subject Re: [ib-support] Re: Exists versus select first
Author Claudio Valderrama C.
""Ivan Prenosil"" <prenosil@...> wrote in message
> This is written in IB documentation (Embedded SQL guide):
> "EXISTS tests that for a given value there is at least one qualifying row
meeting the search condition
> specified in a subquery. The SELECT clause in the subquery must use the *
(asterisk) to select all columns."

Exists() is designed to be fast internally.

> Below is relevant part of older message from Diane Brown.

Diane was only saying that the way to detect if there are records is
implementation dependant. An engine isn't required to test for empty table.
It could be as silly as retrieving all records and then answering. But IB/FB
is as smart as the case requires. And she hinted, too that the standard
caters for specific, field-based rights on SELECT that we don't support.

Claudio Valderrama C. - -
Independent developer
Owner of the Interbase® WebRing