Select * from table where desired period does not overlap with existing periods - mysql

Question

I have a table with records and a period of time for each record, like reservations for instance. So my records look like this:
Table-reservations
id room datefrom dateto
1 'one' '2015-09-07' '2015-09-12'
2 'two' '2015-08-11' '2015-09-02'
3 'three' '2015-06-11' '2015-06-14'
4 'two' '2015-07-30' '2015-08-10'
5 'four' '2015-06-01' '2015-06-23'
6 'one' '2015-03-21' '2015-03-25'
...
n 'nth' '2015-06-01' '2015-07-03'
Also there is a table with rooms containing an ID, a roomnumber and a roomtype, like this:
Table-rooms
idrooms room roomtype
1 'one' 'simple'
2 'two' 'simple'
3 'three' 'double'
...
nx 'nth' 'simple'
As you can see some rooms appear multiple times, but with different periods, because they are booked on various periods.
What I need to obtain through SQL is a list of rooms that are available in a given period of time.
So something like(pseudocode):
Select room from table where there is no reservation on that room between 2015-08-13 and 2015-08-26
How can I do this?
So I will have a fromdate and a todate and I will have to use them in a query.
Can any of you guys give me some pointers please?
Right now I use the following sql to obtain a list of rooms that are available NOW
select * from rooms
where idrooms not in
(
select idroom from rezervations where
((date(now())<=dateto and date(now())>=datefrom)or(date(now())<=dateto and date(now())<=datefrom))
)
order by room

Answer 1

This might be easier to understand.
Assuming you have another table for rooms.
SELECT *
FROM rooms
WHERE NOT EXISTS (SELECT id
FROM reservations
WHERE reservations.room = rooms.id
AND datefrom >= '2015-08-13'
AND dateto <= '2015-08-26')

Answer 2

You'll want to check that records don't exist where 'date from' is less than or equal to the end date in your range and 'date to' is greater than or equal to the start date in your range.
select t1.room
from reservations t1
where not exists (
select *
from reservations t2
where t2.room = t1.room
and t2.datefrom <= '2015-08-26'
and t2.dateto >= '2015-08-13'
)
group by room
You can try it out here: http://sqlfiddle.com/#!9/cbd59/5
I'm new to the site, so it won't let me post a comment, but I think the problem on the first answer is that the operators should be reversed.
As mentioned in a previous comment, this is only good if all of the rooms have a reservation record. If not, better to select from your rooms table like this: http://sqlfiddle.com/#!9/0b96e/1
select room
from rooms
where not exists (
select *
from reservations
where rooms.room = reservations.room
and reservations.datefrom <= '2015-08-26'
and reservations.dateto >= '2015-08-13'
)

Answer 3

SELECT a.room
FROM yourTable a
WHERE a.room NOT IN (
SELECT DISTINCT( b.room )
FROM yourTable b
WHERE datefrom >= '2015-08-13'
OR dateto <= '2015-08-26'
);
It should work to the best of my guesses. If it doesn't; could you please provide a sqlfiddle to check the data on?

Answer 4

Using this SO answer
Consider
range1 : r11 r12 [inputfromDate inputToDate]
range2 : r21 r22 [datefromColumn datetoColumn]
IF r11 <= r22 && r21 <= r12, then the ranges are overlapping.
There are 6 possible case, where two ranges can overlap. But the above two condition itself handles all the 6 possibilities.
If the above condition matches then that means, the dates are overlapping. So I have used not in to get the remaining entries.
select * from <table-name> where id not in (
select id from <table-name> where
:inputfromDate <= datetoColumn and datefromColumn <= :inputToDate
)

Answer 5

You might try this :
select * from rooms
where room not in(
select room from reservations
where '2015-09-16' >= datefrom
and '2015-09-16' <=dateto
and '2015-09-21' >= dateto
)
Goodluck!