insert/update data from one column to another with on conflict update, only those that have different values for specific fields?

I have two columns products/tmp_products with following specification
(id bigint primary key ,price int not null,quantity int not null ,lastupdate timestamp)
I want sql to
                  Insert from tmp_products to products when id not in products.
                  Update only if (price or quantity) values are changed.

INSERT INTO products(id,price,quantity,lastupdate)
            SELECT  (id,price,quantity,lastupdate) FROM tmp_products
    ON CONFLICT (id) DO UPDATE SET
    price=EXCLUDED.price,
    quantity=EXCLUDED.quantity,
    lastupdate=EXCLUDED.lastupdate
    where price!=EXCLUDED.price or quantity!=EXCLUDED.quantity;

I’m getting following error
column reference "price" is ambiguous
I want to know how to approach this problem?

Answer

The problem is in the where clause. You need to qualify the columns so there are unambiguous:

INSERT INTO products(id,price,quantity,lastupdate)
SELECT id,price,quantity,lastupdate FROM tmp_products
ON CONFLICT (id) DO UPDATE SET
    price      = EXCLUDED.price,
    quantity   = EXCLUDED.quantity,
    lastupdate = EXCLUDED.lastupdate
WHERE products.price <> EXCLUDED.price OR products.quantity <> EXCLUDED.quantity;

Note that you also need to remove the parentheses around the SELECT, otherwise your query is not valid Postgres SQL, and would raise error INSERT has more target columns than expressions.