使用SQL匹配特定的一对多条目

Question

Suppose I have two tables:

product
-------
productid
name

and

language
--------
productid
code

I have three products:

1, 'homebody' -> 1, EN
2, 'continetnal' -> 2, FR
                 -> 2, EN
                 -> 2, ES
3, 'westy'       -> 3, EN
                 -> 3, ES
                 -> 3, FR
                 -> 3, PT
4, 'oktoberfest' -> 4, DE

Suppose I have a list of languages I am interested EN, FR, ES in I would like to create three types of query to select a number of products.

1. Match any language in my list ('homebody', 'continental', 'westy')
2. Match all languages in my list ('continental', 'westy')
3. Match exactly languages in my list ('continental')

I think the solution to the first is just:

SELECT * FROM products AS p JOIN language AS l ON (p.productid = l.productid) WHERE l.code IN ('EN', 'ES', 'FR')

What is a good way for me to solve the other queries? I suspect something where I count the number of languages associated with my product and make sure it is equal-to or at-least the number of languages in my query, but not sure how to make this happen.

Answer 1

if you can't have two times FR (or any language) for the same product :

2.

SELECT p.productid, p.name 
FROM products AS p 
JOIN language AS l ON (p.productid = l.productid) 
WHERE l.code IN ('EN', 'ES', 'FR')
GROUP BY p.productid, p.name
HAVING COUNT(*) = 3

3.

WHERE l.code IN ('EN', 'ES', 'FR')
AND NOT EXISTS (SELECT NULL FROM language where productid = p.productid
   AND code NOT IN ('EN', 'ES', 'FR')
GROUP BY p.productid, p.name
HAVING COUNT(*) = 3

or if you wanna retrieve languages codes

SELECT * FROM products p
JOIN language l on p.productid = l.productid
where p.productid IN
  (SELECT p1.productid from product p1
   JOIN language AS l1 ON (p1.productid = l1.productid) 
    WHERE l1.code IN ('EN', 'ES', 'FR')
    GROUP BY p1.productid,
    HAVING COUNT(*) >= 3)

Answer 2

How about the following solutions?

1. Match any language in my list ('homebody', 'continental', 'westy')

    select p.* from product p, language l where p.productid = l.productid and l.code in ('homebody', 'continental', 'westy') 

2. Match all languages in my list ('continental', 'westy')

    select distinct p.* from product p, product p2, language l where p.productid = l.productid and l.code in ('continental', 'westy') and p.productid = p2.productid 

3. Match exactly languages in my list ('continental')

    select p.* from product p, language l where p.productid = l.productid and l.code in ('continental')