How to connect 2 queries SQL - mysql

Question

How to connect these 2 queries to receive one that gives such a response:
user_name room_name_reserved room_name_biggest_time
user_1 room_1 room_2
room_name_reserved - most often reserved room by user
room_name_biggest_time - room when user spent the most time
1 query:
SELECT
us.name as user_name
,ro.name as room_name_reserved
FROM reservation re
INNER JOIN user us on us.id = re.userid
INNER JOIN room ro on ro.id = re.roomid
GROUP BY us.name, ro.name
HAVING COUNT(room_name_reser) = (SELECT COUNT(*) FROM reservation re1
WHERE re1.userid = re.userid
GROUP BY re1.roomid
ORDER BY COUNT(*) DESC
LIMIT 1
)
2 query :
SELECT
us.name as user_name
,ro.name as room_name_biggest_time
from Reservation re
INNER JOIN user us on us.id = re.userid
INNER JOIN room ro on ro.id = re.roomid
WHERE (strftime('%s', re.EndsAt) - strftime('%s', re.StartsAt)) = (SELECT MAX((strftime('%s', re1.EndsAt) - strftime('%s', re1.StartsAt))) as time FROM Reservation re1 where re1.UserId = re.userid
ORDER BY time DESC
LIMIT 1 )

Answer 1

Use the two query as subquery in join
select t1.user_name, t1.room_name_reserved , t2.room_name_biggest_time
from (
select
us.name as user_name,
ro.name as room_name_reserved
from reservation re
inner join user us on us.id = re.userid
inner join room ro on ro.id = re.roomid
group by us.name, ro.name
having count(room_name_reser) = (
select count(*)
from reservation re1
where re1.userid = re.userid
group by re1.roomid
order by count(*) desc
limit 1)
) t1
left join (
select
us.name as user_name,
ro.name as room_name_biggest_time
from Reservation re
inner join user us on us.id = re.userid
inner join room ro on ro.id = re.roomid
Where (strftime('%s', re.EndsAt) - strftime('%s', re.StartsAt)) = (
SELECT Max((strftime('%s', re1.EndsAt) - strftime('%s', re1.StartsAt))) as time
from Reservation re1
where re1.UserId = re.userid
order by time desc limit 1
)
) t2 on t1.user_name = t2.user_name

Answer 2

Assuming you are using MySql, here's a little hack that can work:
SELECT
user_name,
SUBSTRING_INDEX(group_concat(room_name ORDER BY n_reservations DESC), ',', 1) as room_name_reserved,
SUBSTRING_INDEX(group_concat(room_name ORDER BY total_stay DESC), ',', 1) as room_name_biggest_time
FROM (
SELECT
us.name as user_name,
ro.name as room_name,
count(*) as n_reservations,
sum(strftime('%s', re.EndsAt) - strftime('%s', re.StartsAt)) as total_stay
FROM user u
JOIN reservation re on us.id = re.userid
JOIN room ro on ro.id = re.roomid
GROUP BY us.name, ro.name
) t
GROUP BY user_name
Explanation:
With the subquery, aliased as t, we extract the total number of reservations (count(*)) and the total staying time (sum(...)) for each user/room, producing an intermediate output as follows:
user room n_reservations total_stay
--------------------------------------
user1 room1 1 6000
user1 room2 2 3000
user1 room3 1 4000
user2 room2 1 9000
user2 room4 5 4000
With the outer query we GROUP BY user, and for each user we first group concat the room name using a sorting based on counts and sums made before (biggest value first), producing an intermediate output as follow:
user group_concat#1 group_concat#2
---------------------------------------
user1 room2,room1,room3 room1,room3,room2
user2 room4,room2 room2,room4
Last step, we split by comma the output of the two group_concat mantaining only the first value, so final result will be:
user room_name_reserved room_name_biggest_time
-----------------------------------------------
user1 room2 room1
user2 room4 room2