mysql query - how to find items not within certain dates - mysql

Question

I'm pretty useless at SQL it seems and I'm trying to figure out what is the correct query to use.
I have a table Items and a table Reservations. An item can have many reservations and reservations are made between two dates.
I'm trying to create a search query which will return all the Items which don't have reservations between two user inputted dates.
the SQL I have at the minute looks like:
SELECT `Item`.`id`, `Item`.`user_id`, `Item`.`name`, `Item`.`description`, `User`.`id`, `User`.`username`, `User`.`password`, `User`.`email`
FROM `database`.`items` AS `Item`
LEFT JOIN `database`.`reservations` AS `ReservationJoin` ON (`ReservationJoin`.`item_id` = `Item`.`id` AND `ReservationJoin`.`start` >= '2013-07-17' and `ReservationJoin`.`finnish` <= '2013-07-20')
LEFT JOIN `database`.`users` AS `User` ON (`Item`.`user_id` = `User`.`id`)
WHERE ((`Item`.`name` LIKE '%projector%') OR (`Item`.`description` LIKE '%projector%')
AND `ReservationJoin`.`id` IS NULL
LIMIT 10
I'm doing this in cakephp 2.3 so the code looks like:
$this->paginate = array(
"conditions" => array(
"or" => array(
"Item.name LIKE" => '%'.$projector.'%',
"Item.description LIKE" => '%'.$projector.'%',
),
"ReservationJoin.id" => null,
),
"joins" => array(
array(
"table" => "reservations",
"alias" => "ReservationJoin",
"type" => "LEFT",
"conditions" => array(
"ReservationJoin.item_id = Item.id",
"ReservationJoin.checkin >= '{$start}' and ReservationJoin.checkout <= '{$finnish}'",
)
)
),
"limit"=>10
);
$data = $this->paginate('Item');
This isn't working and I think it's to do with the join not excluding the reservations properly. But I've not been able to figure out what the correct mysql is. Can a kind soul tell me what I should be using?
thanks

Answer 1

If something has a reservation between two dates, then one of the following is true:
It has a start date between the dates
It has an end date between the dates
It has a start date before the earlier date and an end date after the second one
The following query uses this logic in a having clause. The approach is to aggregate at the item level and ensure that the three above conditions are true:
SELECT i.`id`, i.`user_id`, i.`name`, i.`description`
FROM `database`.`items`i LEFT JOIN
`database`.`reservations` r
ON r.`item_id` = i.`id`
WHERE ((i.`name` LIKE '%projector%') OR (i.`description` LIKE '%projector%')
group by i.id
having max(start between '2013-07-17' and '2013-07-20') = 0 and
max(finish between '2013-07-17' and '2013-07-20') = 0 and
max(start < '2013-07-17' and finished > '2013-07-20') = 0
LIMIT 10;
Note that none matches are returned, because the conditions are treated as false when start and ned are NULL.

Answer 2

I think it may be easier for you in CakePHP to put all of the conditions in a WHERE clause. (This could also be done with some OUTER JOINs but it may be difficult to transcribe into CakePHP)
SELECT id, user_id, name, description
FROM items
WHERE ((name LIKE '%projector%') OR (description LIKE '%projector%'))
AND NOT EXISTS(
SELECT *
FROM reservations
WHERE items.id = reservations.item_id
AND (
'2013-07-17' BETWEEN start and finnish
OR
'2013-07-20' BETWEEN start and finnish
OR
start BETWEEN '2013-07-17' AND '2013-07-20'));
Or, using the same logic the WHERE clause can be cleaned up to be
SELECT id, user_id, name, description
FROM items
WHERE ((name LIKE '%projector%') OR (description LIKE '%projector%'))
AND NOT EXISTS(
SELECT *
FROM reservations
WHERE items.id = reservations.item_id
AND NOT(
'2013-07-17' > finnish
OR
'2013-07-20' < start
));

Answer 3

you can try this.
SELECT `Item`.`id`, `Item`.`user_id`, `Item`.`name`, `Item`.`description`, `User`.`id`, `User`.`username`, `User`.`password`, `User`.`email`
FROM `database`.`items` AS `Item`
LEFT JOIN `database`.`reservations` AS `ReservationJoin` ON (`ReservationJoin`.`item_id` = `Item`.`id`)
LEFT JOIN `database`.`users` AS `User` ON (`Item`.`user_id` = `User`.`id`)
WHERE ((`Item`.`name` LIKE '%projector%') OR (`Item`.`description` LIKE '%projector%'))
AND `ReservationJoin`.`start` >= '2013-07-17'
AND `ReservationJoin`.`finnish` <= '2013-07-20'
AND `ReservationJoin`.`id` IS NULL
LIMIT 10
i.e just move the date clauses into the WHERE clause as oppose to being in the JOIN CLAUSE