错误 #1242 子查询返回多于 1 行

Question

UPDATE tbl_products
SET Stocks = (Select Stocks 
              WHERE Product_ID IN (3,4,6)) - (SELECT Quantity 
                                              FROM tbl_transactions 
                                              WHERE Product_ID IN (3,4,6) 
                                                AND Date_Time BETWEEN '2020-09-20' AND '2020-09-22');

#1242 - Subquery returns more than 1 row

My problem is, how can I make the "Stocks" accept multiple rows or is it even possible? Is there other solutions besides this? I already run the subquery and it returned 3 rows and I need that 3 rows to be accepted by "Stocks" so it will subtract the values from my first table.

Answer 1

SET stocks can only take one value. Your subquery is returning more than one. Make sure it can only return one value. Run the subquery by itself to confirm.

Answer 2

You should only be assing a single value to a SET of columns. eg

SET a = 'test', b = 'something'

However, if you would like to update multiple rows, you would need INSERT IGNORE or to update all the table rows with a specific value then you would just need to write a proper WHERE condition.