MySQL update a record on duplicate key update (merge) - mysql

Question

I have a table products with the follow schema:
CREATE TABLE `products` (
`id` bigint unsigned NOT NULL AUTO_INCREMENT,
`user_id` bigint unsigned NOT NULL,
`article_id` bigint unsigned NOT NULL,
`price_cents` int unsigned NOT NULL,
`quantity` smallint NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `idx_products_unique` (`user_id`,`article_id`,`price_cents`),
KEY `fk_products_article` (`article_id`),
CONSTRAINT `fk_products_article` FOREIGN KEY (`article_id`) REFERENCES `articles` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT `fk_products_user` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB
Now I can do INSERT with this query:
INSERT INTO `products` (`user_id`,`article_id`,`price_cents`,`quantity`)
VALUES (1,1,200,1)
ON DUPLICATE KEY UPDATE `price_cents`=VALUES(`price_cents`),`quantity`=quantity+VALUES(`quantity`)
So now I have 1 product (ID 1) with quantity 1 and price 200.
Now I insert 2 more products with:
INSERT INTO `products` (`user_id`,`article_id`,`price_cents`,`quantity`)
VALUES (1,1,200,1),(1,1,199,1)
ON DUPLICATE KEY UPDATE `price_cents`=VALUES(`price_cents`),`quantity`=quantity+VALUES(`quantity`)
Now I have 2 products, one (ID 1) with quantity 2 and price 200 and the other (ID 2) with quantity 1 and price 199.
Good.
The problem comes now: I want to update the product with price 199 and set a new price to 200. What I do is:
INSERT INTO `products` (`id`,`user_id`,`article_id`,`price_cents`,`quantity`)
VALUES (2,1,1,200,1)
ON DUPLICATE KEY UPDATE `price_cents`=VALUES(`price_cents`),`quantity`=quantity+VALUES(`quantity`)
and what I would like is a single product with id 1, price 200, and quantity 3, but I get Number:0x426, Message: "Duplicate entry '1-1-200' for key 'products.idx_products_unique' because MySQL does not delete the product with ID 2.
Is there a way to achieve this in MySQL (keep in mind that I want to perform these operations in bulk)?

Answer 1

Don't use id in the statement. A single IODKU does the entire task:
INSERT INTO t (`user_id`,`article_id`,`price_cents`,`quantity`)
...
ON DUPLICATE KEY UPDATE
quantity = quantity + VALUES(quantity)
Where ... is either a batch: VALUES (11,22,33), ... or SELECT (uid,aid,cents) FROM temp.
(Optionally, get rid of id and upgrading the 3-column Unique index to be Primary.)

Answer 2

I think your design does not comply with your intent.
Get rid of
UNIQUE KEY idx_products_unique (user_id,article_id,price_cents),
You can make it a non-unique index if you plan to query by it.
Also - I think you are not using the database correctly...
You should just have the records - raw data with the values.
You should get the value you are trying to aggregate as a view or a query (use group by).

Answer 3

You should use a merge statement, For example:
You have two tables, Products and Products info
You want to merge both but don't want to include duplicates.
Use the Following
MERGE Products P
USING Products_Info PI
ON (PI.ProductID = P.ProductID)
WHEN MATCHED
THEN UPDATE SET
P.Product_Name = PI.Product_Name,
P.Cost = PI.Cost
WHEN NOT MATCHED BY TARGET
THEN INSERT (Product_ID, Product_Name, Cost/quantity)
VALUES(PI.ProductID,PI.Product_Name,PI.Cost)
WHEN NOT MATCHED BY SOURCE
THEN DELETE;