Question

I have a database that contains products, beds to be specific. The details of each bed is stored in a products table, but then I have a separate table, product_bedding_sizes that holds records for each size a bed can in. So one bed may have five entries in this table (it’s a one-to-many relationship).

That bit is done. However, on the public website, visitors can search products and restrict their search to a particular bed size. So my question is, how can I take an array of sizes and select all bed products that may have one or more entries for the specified sizes?

A simplified schema:

CREATE TABLE `products` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `name` (`name`)
) ENGINE=InnoDB;

CREATE TABLE `product_bedding_sizes` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `product_id` int(10) unsigned NOT NULL,
  `size` int(10) unsigned NOT NULL,
  PRIMARY KEY (`id`),
  KEY `product_id` (`product_id`)
) ENGINE=InnoDB;

ALTER TABLE `product_bedding_sizes`
  ADD CONSTRAINT `product_bedding_sizes_ibfk_1`
    FOREIGN KEY (`product_id`)
    REFERENCES `products` (`id`)
    ON DELETE CASCADE
    ON UPDATE CASCADE;

If the user selects say, 90cm and 120cm, the plain English explanation of the query would be:

Select all from the products table where it may have a sizein the product_bedding_sizes table that’s 90cm or 120cm.

Answer 1

I take your requirement to be that a row should be returned if the product has a size of 90 OR if it has a size of 120, or both. (The query would be slightly different to return rows where the product has both size of 90 AND a size of 120.)

Any of these queries return the specified result:

SELECT p.id
     , p.name
  FROM products p
  JOIN product_bedding_sizes s
    ON s.product_id = p.id
   AND s.size IN (90,120)
 GROUP
    BY p.id
     , p.name

–or–

SELECT p.id
     , p.name
  FROM products p
  JOIN ( SELECT s.product_id
           FROM product_bedding_sizes s
          WHERE s.size IN (90,120)
          GROUP BY s.product_id
       ) t
    ON t.product_id = p.id
 ORDER
    BY p.id
     , p.name

— or —

SELECT p.id
     , p.name
  FROM products p
 WHERE EXISTS
       ( SELECT 1
           FROM product_beddings_sizes s
          WHERE s.product_id = p.id
            AND s.size IN (90,120)
       )
 ORDER
    BY p.id
     , p.name

— or —

SELECT p.id
     , p.name
  FROM products p 
 WHERE p.id IN
       ( SELECT s.product_id
           FROM product_bedding_sizes s
          WHERE s.size IN (90,120)
       )
 ORDER
    BY p.id
     , p.name