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Re: Perl DBI MS SQL Question

by sedhed (Scribe)
on Jul 12, 2002 at 22:33 UTC ( #181413=note: print w/replies, xml ) Need Help??


in reply to Perl DBI MS SQL Question

Regarding the first problem (limiting results to page-size subsets with MS SQL), I use a nested select that I picked up from a DBA much craftier than myself, and I use it in code like the following (using an arbitrary 'parts' table with fields 'partno' and 'custno'):

my $perpage = '25'; my $curpage = $q->param('curpage') || 1; # Assumes $q is a CGI object my $custno = $q->param('custno'); my $offset = $curpage*$perpage; my $orderby = 'partno'; my $totalcount = @{ $dbh->selectrow_arrayref( qq{SELECT count(*) FROM parts WHERE custno = '$custno'} ) }[0]; # Next four lines limit the results of the LAST page's data, in case o +f a short page. my $reccount = $perpage; if (($totalcount - $offset) < 0) { $reccount = $totalcount-$offset+$perpage; } # Now build the select (read inside out) (my $select = <<ENDOFSQL) =~ s/^\s*#.*\n//gm; SELECT * FROM ( SELECT top $reccount * FROM ( SELECT top $offset * FROM parts WHERE custno = '$custno' ORDER BY $orderby DESC ) top_data ORDER BY $orderby ASC ) page_data ORDER BY $orderby DESC ENDOFSQL my $dataref = $dbh->selectall_arrayref($select,{Columns=>{}}) || die ' +Whoops!';

The main select gets everything past the $offset, it's then wrapped in a select that flips the order and gets just the TOP $reccount of the first set, in turn that's wrapped in a last outer select which just flips the order back right-side-up.

Anyone else use something like this?

I know I'm wasting a few cycles doing the $totalcount lookup, but I also use that number to generate the page navigation links. In fact, I might ask for critique of my navLinks() sub here at some point, I think it's kinda nifty.

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