MySql - 如何根据在另一个表中加入的多个值从一个表中 select 行

Question

I have two tables, one of products, and the other of product tags

CREATE TABLE IF NOT EXISTS `products` (
  `id` int(6) unsigned NOT NULL,
  `name` varchar(5)  NOT NULL,
PRIMARY KEY (`id`)
) DEFAULT CHARSET=utf8;
INSERT INTO `products` (`id`, `name`) VALUES
  (1,  'Shirt'),
  (2,  'Pants'),
  (3, 'Socks');
CREATE TABLE IF NOT EXISTS `tags` (
  `tag_id` int(6) unsigned NOT NULL,
  `product_id` int(6) unsigned NOT NULL
) DEFAULT CHARSET=utf8;
INSERT INTO `tags` (`tag_id`, `product_id`) VALUES
  (50,  1),
  (51,  1),
  (50, 2);

Fiddle: http://sqlfiddle.com/#!9/3f58a16/1

1 - I need a query that will get all products with ALL tags. There can be a variable number of tagged filtered by. (ex: 50 AND 51 AND... )

SELECT products.id, products.name 
FROM products 
JOIN (
   SELECT product_id, count(DISTINCT tag_id) AS c 
   FROM tags 
   WHERE tags.tag_id IN(50,51) 
   GROUP BY product_id
) t ON t.product_id = products.id 
WHERE t.c = 2

2 - I need a query that will get all products with ANY tags. There can be a variable number of tagged filtered by. (ex: 50 OR 51 OR... )

SELECT products.id, products.name 
FROM products 
JOIN (
   SELECT product_id, count(DISTINCT tag_id) AS c 
   FROM tags 
   WHERE tags.tag_id IN(50,51) 
   GROUP BY product_id
) t ON t.product_id = products.id 

My question is if this is a fine way to go about getting the results I need

products

id | name
1    Shirt    
2    Shoes
3    Pants

tags

product_id | tag_id
1            50
1            51
2            50

Desired result (where tags are 50 AND 51)

id | name
1    Shirt  

• I would be happy to edit the title if someone can suggest better phrasing...

Answer 1

For Case1 You can try the below -

SELECT products.id, products.name 
FROM products join tags on products.id=product_id
where tag_id in (50,51)
group by products.id, products.name
having count(distinct tag_id)=2

For Case2 you don't need the group by with having clause

SELECT distinct products.id, products.name 
FROM products join tags on products.id=product_id
where tag_id in (50,51)

Answer 2

You can use the exists for the first query as follows:

SELECT p.id, p.name 
  FROM products p join tags t on p.id=t.product_id
 where t.tag_id in (50,51)
   And exists
       (Select 1 from tags tt
           Where tt.tag_id in (50,51)
             And tt.tag_id <> t.tag_id
             And tt.product_id = t.product_id)

For second query just use IN as mentioned in other answer.