将mysql中的行从一个表更新到另一个表

Question

I'm trying to run a query that updates rows from one table to another. I want to take the values from shopping_cat_id and put them into existing rows in the table merchants where the ids match.

here is my query thats giving me error 1064..

UPDATE `merchants` SET `category_id`=[shopping_cat_id] WHERE merchants.id = shopping.shopping_id


(SELECT shopping_id, shopping_cat_id FROM shopping)

Answer 1

Try this:

UPDATE merchants m 
    inner join shopping s on 
               m.id = s.shopping_id
   SET m.category_id=s.shopping_cat_id

It should have some where clause of course. Unless you want to update all.