连接表上的SQL查询

Question

我有以下SQL模式：

+----------+
| products |
+----------+
| id       |
| name     |
+----------+
    ^ 8
    |
    v 1
+-------------+
|   values    |
+-------------+
| value       |
| product_id  |
| property_id |
+-------------+
    ^ 8
    |
    v 1
+------------+
| properties |
+------------+
| id         |
| name       |
+------------+

一个产品具有许多属性，而一个属性属于许多产品。 values表是products和properties之间的many_to_many关联的联接表。 并且在此表中保存了产品的属性值。

现在，我正在寻找一个查询，以选择属性x的值为a ，属性y的值为b ecc的所有产品。 我的尝试是此查询，但不返回任何记录：

SELECT DISTINCT 
    products.* 
FROM 
    products 
INNER JOIN 
    product_values 
    ON product_values.product_id = products.id 
INNER JOIN 
    properties 
    ON properties.id = product_values.property_id 
WHERE 
    (properties.name = 'size' AND product_values.value = 'big') 
    AND (properties.name = 'color' AND product_values.value = 'red')

如果可能，我需要一个没有嵌套选择的查询。

Answer 1

由于属性不能同时是color和size ，因此需要在where子句中使用OR 。 然后将数据分组并检查两者是否都在分组having

SELECT products.id, products.name
FROM `products` 
INNER JOIN `product_values` ON `product_values`.`product_id` = `products`.`id` 
INNER JOIN `properties` ON `properties`.`id` = `product_values`.`property_id` 
WHERE (properties.name = 'size' AND product_values.value = 'big') 
   OR (properties.name = 'color' AND product_values.value = 'red')
GROUP BY products.id, products.name
HAVING count(distinct properties.name) = 2

Answer 2

我将使用group by并having ：

select pv.product_id
from product_values pv join
     properties p
     on pv.property_id = p.id
where (p.name, v.value) in ( ('size', 'big'), ('color', 'red') )
group by pv.product_id
having count(distinct p.name) = 2;

Answer 3

使用sum过滤实体的多个属性的另一种方法

SELECT  
  `p`.* 
FROM
  `products` p
  INNER JOIN `product_values` v
    ON `v`.`product_id` = `p`.`id` 
  INNER JOIN `properties`  pr
    ON `pr`.`id` = `v`.`property_id` 
GROUP BY p.id
HAVING SUM (pr.name = 'size' AND v.value = 'big') 
  AND SUM(pr.name = 'color' AND v.value = 'red')