NodeJS + MySQL, UPDATE with a JOIN, ambiguous column name - mysql

Question

First of all, I understand why I'm getting this error message, and I know of a way to solve it, but I'm hoping for something more efficient than what I have in mind. Here is basically what I have:
UPDATE customer c
JOIN customer d ON c.customer_id = d.parent_customer_id
SET ?
WHERE d.customer_type = "Big Cheese";
So, the data being fed in to the "?" parameter looks like this:
{"customer_id": 10, "customer_name": "Cheese-It", ... }
The problem is, since I'm joining on a table that is basically itself, all of the columns have the same name. The only way I know how to fix this is edit the JSON and prefix all of the fields with the alias it needs:
{"c.customer_id": 10, "c.customer_name": "Cheese-It", ... }
I was hoping for a more elegant way of going about this. Is there a way to refactor my SQL so that it knows which table alias I want to update? Any ideas?

Answer 1

A subquery will do what you are wanting, but it's actually less efficient, as subqueries inside the WHERE clause are generally performance killers. I feel like you have to be parsing the JSON into SQL, so I would simply add the alias at that point.
Anyway, for reference, here's how you can refactor the SQL to not need an alias:
UPDATE customer
SET ?
WHERE customer_id IN (
SELECT c.customer_id
FROM customer c
JOIN customer d ON c.customer_id = d.parent_customer_id
WHERE d.customer_type = 'Big Cheese'
);
NOTE: this is untested
EDIT:
On second thought, an EXISTS clause would be slightly better for performance:
UPDATE customer c
SET ?
WHERE EXISTS (
SELECT 1
FROM customer d
WHERE d.parent_customer_id = c.customer_id
AND d.customer_type = 'Big Cheese'
);
Either way should work. As long as you don't have a JOIN in the update, there is only one table the SET columns can reference, so you will avoid the ambiguous column name error.

Answer 2

I know this is an older question, but I found a better solution that doesn't have the performance hit. You can add the alias to your property names in the object you're updating.
Here is the helper function to translate the standard property names with an alias.
const allowUpdate = ['name']
function addUpdateAlias(updated, alias) {
let validUpdate = {}
for (let p in updated) {
if (allowUpdate.indexOf(p) > -1) {
validUpdate[`${alias}.${p}`] = updated[p]
}
}
return validUpdate;
}
Now wrap the object you want to update with the function above and the alias is applied in the update!
Your parameters would then be: [addUpdateAlias(customer, 'c')] to pass into your original query.