MySQL select from many tables with multiple keys and values - mysql

Question

I’m projecting an e-commerce web-app. I have to give the user a set of filters by many goods properties.
In my case, a item in shop may have a many properties, and properties united in collections. For example:
Collection «Bikes» have a «Bryce type» and «Height» properties;
collection «TV» have a «Diagonal» and «Technology».
A items have a property_collection_id key reference to collections table.
The sql query should select a bike with disk braces and height more than 17'', or tv with diagonal more than 100'' and plasma technology (for example).
The table structure is
#
# Sale item
#
CREATE TABLE `object` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`property_collection_id` int(11) DEFAULT NULL,
`price` double DEFAULT NULL,
`description` text COLLATE utf8_unicode_ci,
`state_id` int(11) DEFAULT NULL COMMENT 'State of object, reference to other table',
`created_at` int(11) DEFAULT NULL,
`updated_at` int(11) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `object_to_collection` (`property_collection_id`),
KEY `object_state_fk` (`state_id`),
CONSTRAINT `object_state_fk` FOREIGN KEY (`state_id`) REFERENCES `object_state` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT `object_to_collection` FOREIGN KEY (`property_collection_id`) REFERENCES `property_collection` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
#
# Collection of possible item property
#
CREATE TABLE `property_collection` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`slug_name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL COMMENT 'Name without spaces and punctuation',
`description` text COLLATE utf8_unicode_ci,
`sort` int(11) NOT NULL DEFAULT '100',
`title_field` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
#
# Description of one property
#
CREATE TABLE `property` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`slug_name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`type` enum('boolean','string','integer','list') COLLATE utf8_unicode_ci NOT NULL DEFAULT 'string',
`require` enum('1','0') COLLATE utf8_unicode_ci NOT NULL DEFAULT '0',
`property_collection_id` int(11) DEFAULT NULL,
`sort` int(11) NOT NULL DEFAULT '100',
`units` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `property_to_collection` (`property_collection_id`),
CONSTRAINT `property_to_collection` FOREIGN KEY (`property_collection_id`) REFERENCES `property_collection` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
#
# Item property values
#
CREATE TABLE `property_values` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`object_id` int(11) DEFAULT NULL,
`property_id` int(11) DEFAULT NULL,
`value` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `value_to_object` (`object_id`),
KEY `value_to_property` (`property_id`),
CONSTRAINT `value_to_property` FOREIGN KEY (`property_id`) REFERENCES `property` (`id`),
CONSTRAINT `value_to_object` FOREIGN KEY (`object_id`) REFERENCES `real_estate_object` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=161 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
Code in http://pastebin.com/zJNApskJ
The query that I create is not (and will not) work:
SELECT `object`.* FROM `object`
LEFT JOIN `property_values` ON `object`.`id` = `property_values`.`object_id`
LEFT JOIN `property` ON `property_values`.`property_id` = `property`.`id`
WHERE
(
((`property_values`.`value`='7') AND (`property_values`.`value`='1'))
AND
(CAST(`property_values`.`value` AS DECIMAL) BETWEEN '0' AND '100')
)
AND
(`object`.`property_collection_id`='2') GROUP BY `object`.`id`
How should I create this query?

Answer 1

Your query must reflect the dependency of the tables. Something like
SELECT ...
FROM object o
INNER JOIN property_collections pc ON pc.id = o.property_collection_id
INNER JOIN property p ON p.property_collection_id = pc.id
INNER JOIN property_value pv ON pv.property_id = p.id
WHERE ...
And, as Amdixon already pointed out, you probably meant to say
WHERE pv.value IN ('1','7')
As the original AND condition would always be false. However, I suspect, that you would have to check on the property_collection_id first, in order to make sure, which product type you are actually looking at. Whithout furher data it is impossible to come up with a likely solution.