我有三个数据库表：

products

(

product_id, name etc..

)

specifications

(

id_specification, name

)

product_has_specification

(

id_specification, product_id, specification_value

)

假设我有一件T恤(product_id = 1)，大小M的颜色为蓝色，属性更多 .

我已经尝试加入这三个表并且值= m AND value = blue等 . 但它不显示任何结果 .

我也试过像这样的子查询：

select distinct products.* from products

join product_has_specification on products.id = product_has_specification.product_id

join specifications on product_has_specification.spec_id = pecifications.id_specification

where

(

(specifications.name = 'color' and product_has_specification.value='black')

)

and products.id in

(

select products.id from products

left join product_has_specification on products.id = product_has_specification.product_id

left join specifications on product_has_specification.spec_id = specifications.id_specification

where

(specifications.name='size' and product_has_specification.value='s')

)

如果产品的颜色为“黑色”且尺寸为“s”，则此选择有效;但如果我有更多属性，则说X选择将太长 .

选择怎么样？还有其他解决方案吗？

编辑：

我找到了解决方案 . 它很难看，但它能完成这项工作 . 但是，如果一个产品，让我们说10个规格的查询很长 .

SELECT products.*

FROM products

left JOIN product_has_specification ON products.id = product_has_specification.product_id

left JOIN specifications ON product_has_specification.id_specifiction = specifications.id_specification

WHERE products.id in (

SELECT products.id

FROM products

left JOIN product_has_specification ON products.id = product_has_specification.product_id

left JOIN specifications ON product_has_specification.id_specifiction = specifications.id_specification

where (product_has_specification.value = 'm') and products.id in

(

SELECT products.id

FROM products

left JOIN product_has_specification ON products.id = product_has_specification.product_id

left JOIN specifications ON product_has_specification.id_specifiction = specifications.id_specification

where (product_has_specification.value = 'black') and products.id in

(

SELECT products.id

FROM products

left JOIN product_has_specification ON products.id = product_has_specification.product_id

left JOIN specifications ON product_has_specification.id_specifiction = specifications.id_specification

where (product_has_specification.value = 'test')

)

)

)

group by products.id

使此查询适应您想要的任意数量的规范 . 如果有人有更好的解决方案，请发布 .