如何选择与连接表中定义的条件匹配的记录？

Question

我有这三个表:

products TABLE:
id:integer
name:string

features TABLE:
id:integer
name:string

features_products TABLE:
product_id:integer
feature_id:integer

该features_products TABLE告诉我哪些功能有每个产品.例如:

product_id feature_id
   1         3
   1         5
   3         4

告诉我产品1具有特征3和5,产品3具有特征4,产品2(如​​果存在)没有特征.

我的问题是,我怎样才能SELECT从产品TABLE中获得具有确定功能的所有产品？例如SELECT products which have features 3 AND 5,或SELECT products which have feature 2

Answer 1

要为具有功能3和5的产品选择所有产品ID:

SELECT product_id
FROM features_products
WHERE feature_id IN (3, 5)
GROUP BY product_id
HAVING COUNT(*) = 2

这假定在(product_id,feature_id)上存在唯一性约束.如果您想要产品表中的整行,请在子查询中使用它:

SELECT *
FROM products
WHERE product_id IN (
    SELECT product_id
    FROM features_products
    WHERE feature_id IN (3, 5)
    GROUP BY product_id
    HAVING COUNT(*) = 2
)