+=item sql_taxclass_sameregion
+
+Returns an SQL WHERE fragment or the empty string to search for entries
+with different tax classes.
+
+=cut
+
+#hmm, description above could be better...
+
+sub sql_taxclass_sameregion {
+ my $self = shift;
+
+ my $same_query = 'SELECT taxclass FROM cust_main_county '.
+ ' WHERE taxnum != ? AND country = ?';
+ my @same_param = ( 'taxnum', 'country' );
+ foreach my $opt_field (qw( state county )) {
+ if ( $self->$opt_field() ) {
+ $same_query .= " AND $opt_field = ?";
+ push @same_param, $opt_field;
+ } else {
+ $same_query .= " AND $opt_field IS NULL";
+ }
+ }
+
+ my @taxclasses = $self->_list_sql( \@same_param, $same_query );
+
+ return '' unless scalar(@taxclasses);
+
+ '( taxclass IS NULL OR ( '. #only if !$self->taxclass ??
+ join(' AND ', map { 'taxclass != '.dbh->quote($_) } @taxclasses ).
+ ' ) ) ';
+}
+
+sub _list_sql {
+ my( $self, $param, $sql ) = @_;
+ my $sth = dbh->prepare($sql) or die dbh->errstr;
+ $sth->execute( map $self->$_(), @$param )
+ or die "Unexpected error executing statement $sql: ". $sth->errstr;
+ map $_->[0], @{ $sth->fetchall_arrayref };
+}
+
+=item taxline TAXABLES_ARRAYREF, [ OPTION => VALUE ... ]