DROP PROCEDURE IF EXISTS filldates;
DELIMITER |
CREATE PROCEDURE filldates(dateStart DATE, dateEnd DATE)
BEGIN
  WHILE dateStart <= dateEnd DO
    INSERT INTO helper_days (_day) VALUES (dateStart);
    SET dateStart = date_add(dateStart, INTERVAL 1 DAY);
  END WHILE;
END;
|
DELIMITER ;
CALL filldates('1970-01-01','2038-01-01');

SELECT `_day`
FROM `helper_days`
WHERE (`_day` BETWEEN '2016-02-01' AND '2016-03-01')

SELECT `unit`, `status`, SUM(`quantity`) as `quantity`
FROM `table1` 
WHERE ('2016-02-11' BETWEEN `start` AND `end`)
GROUP BY `unit`, `status, `quantity`

SELECT `unit` , `status` , `quantity` , `start` , `end` 

unit  status quantity           start             end
3 	2 	1 	     2016-02-02 	2016-02-12
3 	2 	1 	     2016-01-16 	2016-02-24
4 	1 	2 	     2016-02-16 	2016-02-26
7 	1 	1 	     2016-02-09 	2016-02-12

day                unit      status   quantity
......
2016-01-02      3         2          2
2016-01-03      3         2          2
.....
2016-01-13      3         2          1
......
2016-01-16      4         1          2

unit  status quantity           start             end
3 	2 	5 	     2016-02-02 	2016-02-12

WHERE ({:дата:} BETWEEN `start` AND `end`)

SELECT `_day`, `unit`, `status`, SUM(`quantity`) AS `quantity`
FROM `helper_days` AS dt
JOIN `table1` AS book  ON `dt`.`_day`  BETWEEN `book`.`start` AND `book`.`end`
WHERE `_day` BETWEEN '2016-01-01' AND '2016-03-01'
GROUP BY `_day`, `unit`, `status`, `quantity`