MySQL: JOIN and WHERE with multiple matches - mysql

Question

I would like to select products from products table with the attributes with id 2 and 5 using the following query:
SELECT `products`.`title`, `products`.`price`
FROM `products`
LEFT JOIN `products_attributes_mapping`
ON `products`.`id` = `products_attributes_mapping`.`product_id`
WHERE
`products_attributes_mapping`.`attribute_value_id` IN (2)
AND `products_attributes_mapping`.`attribute_value_id` IN (5)
GROUP BY `products`.`id`
I expect the product 'Example product 1, blue, size 1' to be returned. But I don't get any result, even though the product with id 1 has attribute_value_id 2 and 5 assigned in the products_attributes_mapping table.
I use IN because I would like to be able to provide multiple attributes, I simplified it only for the example.
SQL fiddle: http://sqlfiddle.com/#!9/2fd94f2/1/0
Schema
CREATE TABLE `products` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`title` varchar(255) CHARACTER SET utf8 NOT NULL,
`price` double NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8mb4;
CREATE TABLE `products_attributes` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4;
CREATE TABLE `products_attributes_mapping` (
`product_id` int(11) NOT NULL,
`attribute_value_id` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
CREATE TABLE `products_attributes_values` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`attribute_id` int(11) NOT NULL,
`name` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8mb4;
Data
INSERT INTO `products` VALUES
(1,'Example product 1, blue, size 1',10),
(2,'Example product 2, yellow, size 1',10),
(3,'Example product 3, black, size 2',15),
(4,'Example product 4, red, size 2',15);
INSERT INTO `products_attributes` VALUES
(1,'Color'),
(2,'Size');
INSERT INTO `products_attributes_mapping` VALUES
(1,2),
(1,5),
(2,4),
(2,5),
(3,3),
(3,6),
(4,1),
(4,6);
INSERT INTO `products_attributes_values` VALUES
(1,1,'red'),
(2,1,'blue'),
(3,1,'black'),
(4,1,'yellow'),
(5,2,'1'),
(6,2,'2'),
(7,2,'3'),
(8,2,'4');

Answer 1

Using aggregation could indeed be a solution. You can use a HAVING clause to ensure that a products has certain attribute values:
SELECT p.title, p.price
FROM products p
INNER JOIN products_attributes_mapping pm ON p.id = pm.product_id
GROUP BY p.id, p.title, p.price
HAVING
MAX(pm.attribute_value_id = 2) = 1
AND MAX(pm.attribute_value_id = 5) = 1
In your DB fiddle, this query returns:
title | price
---------------------------------|-------
Example product 1, blue, size 1 | 10
You can easily extend the expression by adding more AND MAX(...) = 1 conditions.
Another option would be to use a series of WHERE EXISTS conditions with correlated subqueries to search the attributes tables. This is just as good, but will expand as a longer query if you need to add many conditions.