MySQL GROUP_CONCAT within GROUP_CONCAT different Group By values - sql

Question

I am trying to get a group_concat to work within another group_concat but grouped by different values.
3 Tables Products, Customers , and Product_Customer ( which holds what product each customer bought and what size )
#Creates the Customer Table
CREATE TABLE Customer
(
Cus_Code INT AUTO_INCREMENT PRIMARY KEY,
Cus_Name VARCHAR(20)
);
#Creates the Product Table
CREATE TABLE Product
(
Prod_Code INT AUTO_INCREMENT PRIMARY KEY,
Prod_Name VARCHAR(30)
);
#Creates the Product_Customer Table
CREATE TABLE Product_Customer
(
Cus_Code INT references Customer(Cus_Code),
Prod_Code INT references Product(Prod_Code),
Size INT,
);
Sample Data
#Inserts data into Customer Table
INSERT INTO Customer (Cus_Name)
VALUES
('Aaron')
('Bob')
('Charlie')
#Inserts data into Product Table
INSERT INTO Product (Prod_Name)
VALUES
('A')
('B')
('C')
#Inserts data into Product_Customer Table
INSERT INTO Product_Customer (Cus_Code, Prod_Code, Size)
VALUES
(1, 1, 1),
(1, 1, 2),
(1, 2, 1),
(2, 1, 1),
(2, 2, 1),
(2, 2, 2),
(3, 1, 1),
(3, 2, 1),
(3, 3, 1),
(3, 3, 2)
Desired Output Something like this
Customer Name | Product(Size)
Aaron | A(1,2), B(1)
Bob | A(1), B(1,2)
Charlie | A(1), B(1), C(1,2)
So i need the Size grouped by the product_code , then all that grouped by customer code
I have tried with variations of the following but to no avail
SELECT Customer.Cus_Name, GROUP_CONCAT(DISTINCT Product.Prod_Code, '(', s.list, ')' SEPARATOR ', ') AS 'Products'
FROM Product
JOIN (
SELECT Product.Prod_Code AS id, GROUP_CONCAT(DISTINCT Product_Customer.Size SEPARATOR ',') AS list
FROM Product
INNER JOIN Product_Customer ON Product.Prod_Code = Product_Customer.Prod_Code
GROUP BY id;
) AS s ON s.id = Product_Customer.Prod_Code
INNER JOIN Product_Customer ON Product.Prod_Code = Product_Customer.Prod_Code
INNER JOIN Customer ON Product_Customer.Cus_Code = Customer.Cus_Code
GROUP BY Customer.Cus_Code;
It seems to include all the sizes bought for that product, not what size each customer bought.
Any help would be appreciated

Answer 1

SELECT c.Cus_Name,
GROUP_CONCAT(cncat.Size ORDER BY cncat.Prod_Name SEPARATOR ', ') AS Size
FROM Customer c
INNER JOIN
(
SELECT pc.Cus_Code,
p.Prod_Name,
CONCAT(p.Prod_Name, '(', GROUP_CONCAT(pc.size), ')') Size
FROM Product_Customer pc
INNER JOIN Product p
ON pc.Prod_Code = p.Prod_Code
GROUP BY pc.Cus_Code,
p.Prod_Name
) AS cncat
ON c.Cus_Code = cncat.Cus_Code
GROUP BY c.Cus_Name
SQLFiddle Demo

Answer 2

I think the following version will do what you want:
SELECT c.Cus_Name, ps.prodsizes
FROM Customer c JOIN
(select cus_code, group_concat(prod_code, '(', sizes, ')' separator ', ') as prodsizes
from (select pc.cus_code, pc.prod_code, group_concat(distinct p.size separator ',') as sizes
from Product_Customer pc join
Product p
on pc.prod_code = p.prod_code
group by pc.cus_code, pc.prod_code
) cp
group by cus_code
) ps
on ps.cus_code = c.cus_code
GROUP BY c.Cus_Code;
Note that there are two levels of aggregation to get the products and sizes together, first at the customer product level then at the customer level.
I also introduces table aliases to make the query easier to write and read. There is no need for a distinct at the outer level, because duplicates are combined in the subquery.