Question

我有三张桌子：

表产品

ID | NAME
1 | cheese
2 | salami
3 | potato
4 | onion
5 | ananas

表格组件

ID | product_id | component_id
1 | 1 | 1
2 | 1 | 5
3 | 2 | 1
4 | 3 | 5
5 | 3 | 3

表product_components

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我想只买披萨奶酪和凤梨（披萨A）。我该怎么做？

Answer 1

您需要使用Group By和Having子句

select p.Name 
from product_components pc 
inner join product p on pc.ID_PIZZA = p.id
where name in ('cheese' ,'salami')
Group by p.Name
having count(distinct pc.Name)= 2

上述查询将返回同时包含'cheese'和'salami'的Pizza。但同样的披萨也可以有其他一些成分。

或者如果您想要只有'cheese'和'salami'的披萨，那么您需要稍微调整Having子句

select p.Name 
from product_components pc 
inner join product p on pc.ID_PIZZA = p.id
Group by p.Name
having sum(case when name in ('cheese' ,'salami') then 1 else 0 end) = count(*)

Answer 2

SELECT P.Name FROM product P
INNER JOIN (SELECT ID_PIZZA, GROUP_CONCAT(name ORDER BY name) AS INGR
            FROM product_components
            GROUP BY ID_PIZZA
           ) t
ON T.ID_PIZZA = P.ID
AND T.INGR = 'cheese,salami'

Answer 3

select p.name
from product p
join product_components c1 on c1.id_pizza = p.id
join product_components c2 on c2.id_pizza = p.id
where c1.name = 'cheese'
  and c2.name = 'salami'

如果您想要排除不仅仅包含奶酪和萨拉米香肠的比萨饼，您可以使用“不包括LEFT JOIN”扩展查询：

select p.name
from product p
join product_components c1 on c1.id_pizza = p.id
join product_components c2 on c2.id_pizza = p.id
left join product_components other
  on  other.id_pizza = p.id
  and other.name not in (c1.name, c2.name)
where c1.name = 'cheese'
  and c2.name = 'salami'
  and other.name is null

更新

对于更改的架构，查询类似于

select p.name
from products p
join product_components pc1 on pc1.product_id = p.id
join components         c1  on c1.id = pc1.component_id
join product_components pc2 on pc2.product_id = p.id
join components         c2  on c2.id = pc2.component_id
where c1.name = 'cheese'
  and c2.name = 'salami'

select p.name
from products p
join product_components pc1 on pc1.product_id = p.id
join components         c1  on c1.id = pc1.component_id
join product_components pc2 on pc2.product_id = p.id
join components         c2  on c2.id = pc2.component_id
left join product_components pco
  on  pco.product_id = p.id
  and pco.component_id not in (pc1.component_id, pc2.component_id)
where c1.name = 'cheese'
  and c2.name = 'salami'
  and pco.component_id is null

如何在一列中选择两个条件

3 个答案:

更新