How to find if a list/set is contained within another list

问题

I have a list of product IDs and I want to find out which orders contain all those products. Orders table is structured like this:

order_id | product_id
----------------------
1        | 222
1        | 555
2        | 333

Obviously I can do it with some looping in PHP but I was wondering if there is an elegant way to do it purely in mysql. My ideal fantasy query would be something like:

SELECT order_id
FROM orders
WHERE (222,555) IN GROUP_CONCAT(product_id)
GROUP BY order_id

Is there any hope or should I go read Tolkien? :) Also, out of curiosity, if not possible in mysql, is there any other database that has this functionality?

回答1:

You were close

SELECT order_id
FROM orders
WHERE product_id in (222,555) 
GROUP BY order_id
HAVING COUNT(DISTINCT product_id) = 2

Regarding your "out of curiosity" question in relational algebra this is achieved simply with division. AFAIK no RDBMS has implemented any extension that makes this as simple in SQL.

回答2:

I have a preference for doing set comparisons only in the having clause:

select order_id
from orders
group by order_id
having sum(case when product_id = 222 then 1 else 0 end) > 0 and
       sum(case when product_id = 555 then 1 else 0 end) > 0

What this is saying is: get me all orders where the order has at least one product 222 and at least one product 555.

I prefer this for two reasons. The first is generalizability. You can arrange more complicated conditions, such as 222 or 555 (just by changing the "and" to and "or"). Or, 333 and 555 or 222 without 555.

Second, when you create the query, you only have to put the condition in one place, in the having clause.

回答3:

Assuming your database is properly normalized, i.e. there's no duplicate Product on a given Order

Mysqlism:

select order_id
from orders
group by order_id
having sum(product_id in (222,555)) = 2

Standard SQL:

select order_id
from orders
group by order_id
having sum(case when product_id in (222,555) then 1 end) = 2

If it has duplicates:

CREATE TABLE tbl
    (`order_id` int, `product_id` int)
;

INSERT INTO tbl
    (`order_id`, `product_id`)
VALUES
    (1, 222),
    (1, 555),
    (2, 333),
    (1, 555)
;

Do this then:

select order_id
from tbl
group by order_id
having count(distinct case when product_id in (222,555) then product_id end) = 2

Live test: http://www.sqlfiddle.com/#!2/fa1ad/5

回答4:

CREATE TABLE orders
        ( order_id INTEGER NOT NULL
        , product_id INTEGER NOT NULL
        );
INSERT INTO orders(order_id,product_id) VALUES
 (1, 222 ) , (1, 555 ) , (2, 333 )
, (3, 222 ) , (3, 555 ) , (3, 333 ); -- order#3 has all the products

CREATE TABLE products AS (SELECT DISTINCT product_id FROM orders);

SELECT *
FROM orders o1
   --
   -- There should not exist a product
   -- that is not part of our order.
   --
WHERE NOT EXISTS (
        SELECT *
        FROM products pr
        WHERE 1=1
           -- extra clause: only want producs from a literal list
        AND pr.product_id IN (222,555,333)
           --  ... that is not part of our order...
        AND NOT EXISTS ( SELECT *
                FROM orders o2
                WHERE o2.product_id = pr.product_id
                AND o2.order_id = o1.order_id
                )
        );

Result:

 order_id | product_id 
----------+------------
        3 |        222
        3 |        555
        3 |        333
(3 rows)

来源：https://stackoverflow.com/questions/12652037/how-to-find-if-a-list-set-is-contained-within-another-list

标签

mysql

sql

relational-division