essej1 has asked for the wisdom of the Perl Monks concerning the following question:

I'm using the DBI fetchall_arrayref to get the rows from an Oracle SQL statement. (I'm using this one as I do not expect many hits.) There are valid conditions when now rows are found. 

  my $result_array  = $sth->fetchall_arrayref;
  foreach my $row (@{$result_array}) {
    print join (",", @$row),"\n";
    print FH join (",", @$row),"\n";
  }

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If I put 
  print "==>@{$result_array}<==\n";

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after the fetchall I get "==><==" which indicates an empty string. Testing for this with the following doesn’t seem to work. 
  if (@{$result_array} eq “”) {
    <some message>
  } else {
    <do the output>
  }

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How do I test for the "nothing here" condition.
Paradise: Florida, full tank of gas, no appointments.

Replies are listed 'Best First'.
Re: no rows returned for dbi fetchall_arrayref
by toolic (Bishop) on May 07, 2013 at 16:30 UTC
    This should suffice: 
    if ($result_array) {
    print "something\n";
}
else {
    print "nothing\n";
}

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    Also, the DBI POD mentions checking $sth->err

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      Thanks toolic, exactly what I needed. I had the DOH moment just as I opened your response.
      Paradise: Florida, full tank of gas, no appointments.
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Re: no rows returned for dbi fetchall_arrayref
by Random_Walk (Prior) on May 07, 2013 at 16:37 UTC

    In one case you stringified it. In the other you are taking it in scalar context and Perl magic is not doing what you expect. 

    use strict; use warnings; use 5.010;

my @array = qw (there is some data here);
is_empty (\@array);

# look out for edge cases
@array = qw(one);
is_empty(\@array); 

#empty it
@array = ();
is_empty (\@array);

sub is_empty {
    my $array_ref = shift; 
    say "\nGot: ". join ", ", @{$array_ref};
    say "Empty" unless scalar @{$array_ref};
    say "Caution"           if $#{$array_ref}     ==  0;
    say "Empty"             if $#{$array_ref}     ==  -1;
    say "Maths == String?"  if @{$array_ref}      ==  "";
    say "Empty as String?"  if @{$array_ref}      eq  "";
}

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    Cheers,
    R.

    Pereant, qui ante nos nostra dixerunt!
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Re: no rows returned for dbi fetchall_arrayref
by ruzam (Curate) on May 08, 2013 at 04:08 UTC

    fetchall_arrayref returns zero if the query failed

    my $result_array  = $sth->fetchall_arrayref;

if (!$result_array) {
   print "query failed!!\n";
}

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    If no rows are found (the query is successful, but no rows are returned) fetchall_arrayref returns a reference to an empty array.

    my $result_array = $sth->fetchall_arrayref;

if ($result_array) {
    print "success\n";
    if (@$result_array) {
        print "found rows @$result_array\n";
    }
    else {
        print "no rows returned\n";
    }
}
else {
    print "query failed!!\n";
}

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