How to write condition for subquery alias if having null value - mysql

Question

Here is my query,
SELECT
`h`.`hotel_id`,
(
SELECT COUNT(room_id)
FROM
`abserve_hotel_rooms` AS `rm`
WHERE
`rm`.`adults_count` >= "1" AND `rm`.`room_count` >= "1" AND "Available" = IF(
check_in_time = '2016-03-15',
'Unavailable',
(
IF(
'2016-03-15' > check_in_time,
(
IF(
'2016-03-15' < check_out_time,
'Unavailable',
'Available'
)
),
(
IF(
'2016-03-22' > check_in_time,
'Unavailable',
'Available'
)
)
)
)
) AND `room_prize` BETWEEN '174' AND '600' AND `rm`.`hotel_id` = `h`.`hotel_id`
) AS `avail_room_count`,
(
SELECT MIN(room_prize)
FROM
`abserve_hotel_rooms` AS `rm`
WHERE
`rm`.`adults_count` >= "1" AND `rm`.`room_count` >= "1" AND "Available" = IF(
check_in_time = '2016-03-15',
'Unavailable',
(
IF(
'2016-03-15' > check_in_time,
(
IF(
'2016-03-15' < check_out_time,
'Unavailable',
'Available'
)
),
(
IF(
'2016-03-22' > check_in_time,
'Unavailable',
'Available'
)
)
)
)
) AND `room_prize` BETWEEN '174' AND '600' AND `rm`.`hotel_id` = `h`.`hotel_id`
) AS `min_val`
FROM
`abserve_hotels` AS `h`
WHERE
1 AND `city` = "madurai" AND `country` = "india"
It totally return one column values from my table abserve_hotels which is hotel_id with extra two alias columns such as avail_room_count and min_val..
And I wrote those in a subquery..
Here I have to check a condition WHERE min_val IS NOT NULL .i.e; if min_val having NULL value I have to restrict it
How can I do this..
And this is my table
hotel_id avail_room_count min_val
1 0 NULL
2 0 NULL
Here I need to restrict these NULL values..
Someone please help me ..

Answer 1

Add a HAVING clause at the end:
HAVING min_val IS NOT NULL
The new query after WHERE looks like:
WHERE
1 AND `city` = "madurai" AND `country` = "india"
HAVING min_val IS NOT NULL

Answer 2

Your query is overly complex and can be much simplified:
The two correlated sub queries are exactly the same, except for the SELECT list (MIN versus COUNT), so they could be combined into one;
The aggregation done by the sub query can be done in the main query;
The condition for checking availability can be written much shorter.
In fact, you can do all of what you need with the following query:
SELECT h.hotel_id,
COUNT(rm.room_id) as avail_room_count,
MIN(rm.room_prize) AS min_val
FROM abserve_hotels AS h
INNER JOIN abserve_hotel_rooms AS rm
ON rm.hotel_id = h.hotel_id
WHERE h.city = "madurai"
AND h.country = "india"
AND rm.adults_count >= 1
AND rm.room_count >= 1
AND rm.room_prize BETWEEN 174 AND 600
AND ( rm.check_in_time >= '2016-03-22'
OR rm.check_out_time <= '2016-03-15'
OR rm.check_in_time IS NULL)
GROUP BY h.hotel_id
Because the INNER JOIN requires at least one match, you can already be sure that min_val will never be NULL.
The check for availability is just as simple as:
( rm.check_in_time >= '2016-03-22'
OR rm.check_out_time <= '2016-03-15'
OR rm.check_in_time IS NULL)
The three parts of that condition mean:
The reservation for this room is future and does not overlap with this week;
The reservation for this room is in the past, the room is free today at the latest;
The room has no known reservation.
In all three cases the room is available for reservation for the concerned week.