Last 10 record and Sort (PROCEDURE + Variable LIMIT)

/*
 * 1. select last 10 record and sort.
 * 2. calc (`rowsA` + `rowsB`) / `rowsC`.
 * 3. use PROCEDURE and Variable LIMIT.
 */

DROP PROCEDURE IF EXISTS last_10_sort;

DELIMITER //

CREATE PROCEDURE last_10_sort()
BEGIN
    DECLARE record_total, record_from INT DEFAULT 0;
    SET @record_total = (SELECT COUNT(record_time) FROM tableA);
    SET @record_from = (@record_total - 10);

    IF @record_total < 10 THEN
        SELECT `record_time`, round(((`rowsA` + `rowsB`) / (SELECT rowsC FROM tableB WHERE bid = '1') * 100), 2) AS 'tmp' FROM tableA ORDER BY `record_time` LIMIT 10;
    ELSE
        PREPARE stmt_last_10_sort FROM
        "select `record_time`, round(((`rowsA` + `rowsB`) / (select rowsC from tableB where bid = '1') * 100), 2) as 'tmp' from tableA order by `record_time` limit ?, ?";
        EXECUTE stmt_last_10_sort USING @record_from, @record_total;
        DEALLOCATE PREPARE stmt_last_10_sort;
    END IF;
END //
DELIMITER ;

CALL last_10_sort();