"Practical SQL function Group_conca" I know you want to use GROUP_CONCAT with count, like the number of people in different combinations?

Background

A few days ago to review the MySQL function, know that a group_concat function is very useful, but has not actually used. Today, I had a problem and asked me to be a prick. Suppose there is a purchase Product Delta table order_list.

ALTER TABLE pet drop column User2_id;insert into pet (User_id,pet_id,id) VALUES (2, ' a ', 1), (3, ' B ', 1), (4, ' C ', 2), (5, ' a ', 2), (6, ' A ', 3), (7, ' B ', 2), (8, ' C ', 2), (9, ' D ', 1);

/*

Inquire about all products purchased by each user_id (de-weight)

Select O. user_id , Group_concat (Distinct o. product_id ORDER by O. product_id ASC SEPARATOR ') from Order_list o
GROUP by O.user_id

Description: 1.group_concat in the distinct is not necessary, not just do not go heavy; 2. ORDER by O. product_idASC is not required, the default is the merged part is in ascending order, want to in descending order can use desc;3. SEPARATOR ' is also not required and is separated by commas by default. For example:

SELECT o. user_id , Group_concat (o. product_id ) From Order_list o
GROUP by O.user_id
*/

/*

Find out how many different product combinations have multiple products at the same time.

Select T.product_group,count (t.user_id) from
(Select O. user_id , Group_concat (Distinct o. product_id ORDER by O. product_id ASC SEPARATOR ') ' Product_group ' from Order_list o
GROUP by O.user_id
) T
GROUP BY T.product_group

*/

Query A/b/c/d/ab/ac/ad/bc/bd/cd/abc .... How many people are there in a 4+6+4+1=15 combination?

Select O. product_id , COUNT (distinct o.id) from Order_list o
GROUP by O.product_id
Union
Select from

"Practical SQL function Group_conca" I know you want to use GROUP_CONCAT with count, like the number of people in different combinations?