COUNT function not counting correctly with DATEDIFF

Question

I am sure this is a simple fix, but can not figure it out. I have a COUNT function that needs to count the total number of Rentals. Alone, the function works just fine. I have tried using DISTINCT, tweaking the GROUP BY, and ORDER BY, but to not avail.

When I add the DATEDIFF function to get the NumberofDays rented, the COUNT function does not work the way as intended. I should be getting some results with "2" instead of "1". Note that I need to order by the Rentals.Boat_ID. Here is my code and table results. Thanks

SELECT
    BOATS.Boat_Brand,
    COUNT(RENTALS.Boat_ID) AS NumberofRentals,
    DATEDIFF(Day, RENTALS.Rental_StartDay, RENTALS.Rental_EndDay)+1) as NumberofDaysRented
FROM RENTALS
INNER JOIN BOATS
    ON RENTALS.Boat_ID = BOATS.Boat_ID 
GROUP BY
    BOATS.Boat_Brand,
    RENTALS.Rental_StartDay,
    RENTALS.Rental_EndDay
ORDER BY
    COUNT(RENTALS.Boat_ID) DESC;

Boat_Brand	NumberofRentals	NumberofDaysRented
Blue Martin	1	20
Blue Martin	1	35
Boston	1	52
Cherubini	1	11
Dufour	1	10
Eagle Craft	1	19
Motor Yacht	1	17
Motor Yacht	1	47
Grady-White	1	1
Horizon	1	22
Lemsteraak	1	19
Lund	1	64
Mastercraft	1	19
Mastercraft	1	1
Nauticat	1	10
Tracker	1	18
Tracker	1	1
Viking	1	20
Yamaha	1	20

EXPECTED TABLE/RESULTS:

Boat_Brand	NumberofRentals	NumberofDaysRented
Blue Martin	2	55
Motor Yacht	2	64
Mastercraft	2	20
Tracker	2	19
Boston	1	52
Cherubini	1	11
Dufour	1	10
Eagle Craft	1	19
Grady-White	1	1
Horizon	1	22
Lemsteraak	1	19
Lund	1	64
Nauticat	1	10
Viking	1	20
Yamaha	1	20

Answer 1

seems like you need to group only by brand and get sum of rented days :

SELECT
    BOATS.Boat_Brand,
    COUNT(RENTALS.Boat_ID) AS NumberofRentals,
    SUM(DATEDIFF(Day,RENTALS.Rental_StartDay,RENTALS.Rental_EndDay) + 1)) as NumberofDaysRented
FROM
    RENTALS
    INNER JOIN BOATS ON RENTALS.Boat_ID = BOATS.Boat_ID
GROUP BY
    BOATS.Boat_Brand
ORDER BY
    COUNT(RENTALS.Boat_ID) DESC;