#Delete private lists without owner that now have no shares anymore
$query="DELETE vs.* FROM virtualshelves vs LEFT JOIN virtualshelfshares sh USING (shelfnumber) WHERE category=1 AND vs.owner IS NULL AND sh.shelfnumber IS NULL";
$dbh->do($query);
 
#Change owner for private lists which have shares
$query="UPDATE virtualshelves LEFT JOIN virtualshelfshares sh USING (shelfnumber) SET owner=NULL where owner=? AND category=1 AND sh.borrowernumber IS NOT NULL";
$dbh->do($query,undef,($borrower));
 
 
#Handle public lists owned by borrower
$query="UPDATE virtualshelves SET owner=NULL WHERE owner=? AND category=2";
$dbh->do($query,undef,($borrower));
 
#Niet nodig vanwege table constraint..
$query="UPDATE virtualshelfcontents SET borrowernumber=NULL WHERE borrowernumber=?";
$dbh->do($query,undef,($borrower));