Re: Keeping Order with mySQL (Mildly OT)

[Masem]

If you don't mind a few extra SQL calls, you can do a pseudo linked-list; that is, have each element have a 'previous' entry that points to the unique ID of the next element in the list, or NULL if this is the first entry. Then you can do a loop over a SQL statement such as:

my @order;
my $sth_1 = $dbh->prepare( "SELECT id FROM TABLE WHERE previous IS NUL
+L" ) or die $DBI->errstr;
my $sth_2 = $dbh->prepare( "SELECT id FROM TABLE WHERE previous IS ?" 
+) or die $DBI->errstr;
$sth_1->execute() or die $DBI->errstr;
if ( $sth_1->rows() > 0 ) {
    my ($id) = $sth_1->fetchrow_array();
    push @order, $id;
    $sth_2->execute( $id ) or die $DBI->errstr;
    while ( $sth_2->rows() > 0 ) {
       my ( $id ) = $sth_2->fetchrow_array();
       push @order, $id;
       $sth_2->execute( $id ) or die $DBI->errstr;
    }
}

(That code could probably be optimized for logic of course.)

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Dr. Michael K. Neylon - [e-mail] || "You've left the lens cap of your mind on again, Pinky" - The Brain
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