Question

my $sth = $dbh->prepare("SELECT id 
                           FROM user 
                          WHERE group == '1' 
                       ORDER BY id DESC 
                          LIMIT 1");

I was trying to get the id of the last row in a table without reading the whole table.

I am already accessing via:

my $sth = $dbh->prepare("SELECT name,
                                group 
                           FROM user 
                          WHERE group == '1' 
                          LIMIT $from, $thismany");
$sth->execute();
while(my ($name,$group) = $sth->fetchrow_array()) {

…and setting up a little pagination query as you can see.

But, I am trying to figure out how to detect when I am on the last (<= 500) rows so I can turn off my “next 500” link. Everything else is working fine. I figured out how to turn off the “previous 500” link when on first 500 page all by myself!

I thought I would set up a “switch” in the while loop so if ($id = $last_id) I can set the “switches” var.

Like:

if ($id = $last_id) {
$lastpage = 1; #the switch
}

So I can turn off next 500 link if ($lastpage == 1).
I am really new to this and keep getting stuck on these types of things.

Thanks for any assistance.

Answer 1

Try to grab an extra row and see how many rows you really got. Something like this:

my @results = ( );
my $total   = 0;
my $sth     = $dbh->prepare(qq{
        SELECT name, group 
        FROM user 
        WHERE group = ?  
        LIMIT ?, ?
});
$sth->execute(1, $from, $thismany + 1);
while(my ($name, $group) = $sth->fetchrow_array()) {
        push(@results, [$name, $group]); # Or something more interesting.
        ++$total;
}
$sth->finish();  

my $has_next = 0;
if($total == $thismany + 1) {
    pop(@results);
    $has_next = 1;
}

And BTW, please use placeholders in all of your SQL, interpolation is fraught with danger.