当右表中有很多匹配行时左连接

Question

我有两个表。

Product(id, name) 
LineItem(id, product_id, order_id) 
Order(id, state) 

订单可以有很多产品。一个产品可以同时属于多个订单。

我想选择没有特定状态（即1,2）的订单的产品。

我的查询是

SELECT products.id, products.price 
    FROM "products" 
    LEFT OUTER JOIN line_items ON line_items.product_id = products.id 
    LEFT OUTER JOIN orders ON orders.id = line_items.order_id AND orders.status IN (1, 2) 
    WHERE (products.price > 0) AND (orders.id IS NULL) AND "products"."id" = $1 
    GROUP BY products.id, products.price [["id", 11]] 

11是一个产品，是不应该出现的结果的ID，但它确实。

Answer 1

I would like to select Products, which don't have orders with specific statuses(i.e. 1, 2).

SELECT * FROM products p -- I would like to select Products 
WHERE NOT EXISTS(   -- , which don't have 
    SELECT * 
    FROM orders o   -- orders 
    JOIN line_items li ON li.order_id = o.id 
    WHERE li.product_id = p.id 
    AND o.status IN (1,2) -- with specific statuses(i.e. 1, 2). 
    ); 

Answer 2

select p.id, p.name 
from products p 
join lineitem l on l.product_id = p.id 
join `order` o on l.order_id = o.id 
group by p.id, p.name 
having sum(case when o.state in (1,2) then 1 else 0 end) = 0 

Answer 3

的想法是先从产品表并使用left join找到订单，1或2，如果它们不存在，那么你想要的产品：

select p.id, p.name 
from product p left join 
    lineitem li 
    on li.product_id = p.id left join 
    orders o -- a better name for the table 
    on li.order_id = o.id and 
     o.state in (1, 2) 
where o.id is null 
group by p.id, p.name;