获取mysql中所有值的总和

Question

Let's say I have the following table.

mysql> desc items;
+---------------+------------------------+------+-----+---------+-------+
| Field         | Type                   | Null | Key | Default | Extra |
+---------------+------------------------+------+-----+---------+-------+
| item_value    | int(11)                | YES  |     | NULL    |       |
| item_quantity | smallint(5)            | YES  |     | NULL    |       |
+---------------+------------------------+------+-----+---------+-------+

The current SQL statement is simple for items with quantity of 1.

select sum(item_value) as total_value from items where user_id = ?

If a row has more than 1 quantity, I would like to take that into account when I add up the values for all users. Would it be easier to keep track of the total amount per row ( item_quantity * item_value ) or can I do it within a SQL statement?

Answer 1

您可以在sum()语句中进行算术运算：

select sum(item_quantity * item_value) as total_value from items where user_id = ?