RE: howto figure out if ResultSet is empty

["Richard Dettinger" <cujo@xxxxxxxxxx>]

re: I think that if no rows are returned, rather
than an empty ResultSet you get a null one;

No, you should get a ResultSet which is empty.  Calling next() the first
time will return false.  So the
code example below will always work.  If you needed to know to do something
different when it was
empty, you could probably either keep a int count inside your while loop
which you checked after
the loop ended (if the int was still 0, it was null).

Or perhaps something like this:

int i;
for (i = 0; rs.next(); i++) {
      // process row.
}

if (i == 0) {
      // handle empty case.
}

There are other things that should work as well with scrollable resultSets.
(such as using
first() or isBeforeLast()), but my experience is that different drivers
would be more spotty
and less consistant in this area and something like the above solution is a
better idea.

Richard D. Dettinger
iSeries Java Data Access Team

Democracy's enemies have always underestimated the courage of the American
people.
It was true at Concord Bridge.  It was true at Pearl Harbor.  And it was
true today.

         Rochester Post-Bulletin
         Tuesday September 11, 2001


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Mihael Knezevic wrote:

> howto figure out if ResultSet is empty ?
>
> my code looks like this:
>
> Statement statement;
> ResultSet rs;
>
> String stm = "Select xxx from xxx.xxx where xxx";
>
> rs = statement.executeQuery(stm);
>
> while(rs.next())
> {
>            do.something();
> }

I'm not entirely sure, but I think that if no rows are returned, rather
than an empty ResultSet you get a null one; so just test it for null
first.  As well as that, if there is no row available (presumably, even
if there are no rows to begin with) next() should return false.

Cheers,

Martin.

--
Martin McCallion
Senior Technical Consultant
Work:  martin.mccallion@misys.com
Home: martin.mccallion@ukonline.co.uk
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