MySQL从3个表中选择不同的产品

Question

MySQL从3个表中选择.

我有这5个表:

CREATE TABLE `category` (
  `c_id` int(6) NOT NULL AUTO_INCREMENT,
  `name` varchar(40) NOT NULL,
  PRIMARY KEY (c_id)
);

CREATE TABLE `product` (
  `p_id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(40) NOT NULL,
  `brand` varchar(30) NOT NULL,
  `image_path` varchar(100) DEFAULT NULL,
  PRIMARY KEY (p_id)
);

CREATE TABLE `shop` (
  `s_id` int(6) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) NOT NULL,
  `country` varchar(30) NOT NULL,
  `province` varchar(30) NOT NULL,
  `city` varchar(30) NOT NULL,
  `suburb` varchar(30) NOT NULL,
  `street` varchar(40) DEFAULT NULL,
  `streetNumber` varchar(40) DEFAULT NULL,
  `postalCode` int(4) DEFAULT NULL,
   PRIMARY KEY (s_id)
) ;

CREATE TABLE product_category (
p_id INT NOT NULL, 
c_id INT NOT NULL, 
PRIMARY KEY (p_id, c_id), 
FOREIGN KEY (p_id) REFERENCES Product(p_id) ON UPDATE CASCADE, 
FOREIGN KEY (c_id) REFERENCES Category(c_id) ON UPDATE CASCADE
);

CREATE TABLE product_shop (
p_id INT NOT NULL, 
s_id INT NOT NULL, 
PRIMARY KEY (p_id, s_id), 
FOREIGN KEY (p_id) REFERENCES product(p_id) ON UPDATE CASCADE, 
FOREIGN KEY (s_id) REFERENCES shop(s_id) ON UPDATE CASCADE
);

基本上,产品可以有许多类别.可以为许多产品分配类别.一家商店可以有很多产品.一个产品可以在许多商店.

我想选择category.c_id = 2或category.c_id = 8以及shop.s_id = 1或shop.s_id = 2的所有产品.

我对此有所帮助:

select *
from product inner join product_category
on product_category.p_id=product.p_id
where (product_category.c_id=2)
or (product_category.c_id=8)

这将获得类别ID为2的所有产品以及类别ID为8的产品,但如果它同时包含category.c_id = 8和category.c_id = 2,则会获得相同的产品两次.

然后我试着让它变成独特的产品:

select DISTINCT(product.p_id) as product
from product inner join product_category
on product_category.p_id=product.p_id
where (product_category.c_id=2)
or (product_category.c_id=8)

现在哪个不同但没有显示有关产品或类别的足够信息.我希望在每一行中尽可能多地显示信息.

下一步是只获取shop.s_id = 1或shop.s_id = 2的那些.

任何人都可以帮我到那儿或靠近吗？谢谢!

Answer 1

假设您要列出所有产品信息。如果不希望产品重复，可以使用 IN 子句。

select p.*
from product p
where p.p_id in (select c.p_id from product_category c where c.c_id in (2,8))
  and p.p_id in (select s.p_id from product_shop s where s.s_id in (1,2))

现在，如果您想要所有产品数据并列出该产品与哪些类别和商店相关，那么您可以使用 join 和一些非常方便的功能。

select p.p_id, p.`name`, p.brand, GROUP_CONCAT(DISTINCT c.c_id SEPARATOR ', ') as categories, GROUP_CONCAT(DISTINCT s.s_id SEPARATOR ', ') as shops
from product p inner join product_category c on p.p_id = c.p_id
               inner join product_shop s on p.p_id = s.p_id
where c.c_id in (2,8)
  and s.s_id in (1,2)
group by p.p_id, p.`name`, p.brand