build_value example

'_wp_mysql_week' => array( 'week', 'w' ),
            'DAYOFYEAR'      => array( 'dayofyear' ),
            'DAYOFMONTH'     => array( 'day' ),
            'DAYOFWEEK'      => array( 'dayofweek' ),
            'WEEKDAY'        => array( 'dayofweek_iso' ),
        );

        // Check of the possible date units and add them to the query.         foreach ( $date_units as $sql_part => $query_parts ) {
            foreach ( $query_parts as $query_part ) {
                if ( isset( $query[ $query_part ] ) ) {
                    $value = $this->build_value( $compare, $query[ $query_part ] );
                    if ( $value ) {
                        switch ( $sql_part ) {
                            case '_wp_mysql_week':
                                $where_parts[] = _wp_mysql_week( $column ) . " $compare $value";
                                break;
                            case 'WEEKDAY':
                                $where_parts[] = "$sql_part( $column ) + 1 $compare $value";
                                break;
                            default:
                                $where_parts[] = "$sql_part( $column ) $compare $value";
                        }