SUB TOTAL WITH MULTIPLE TABLE - sql

Question

I want to show the subtotals of each product name and maybe the commands I made are useless,
is there any suggestions for me
I have 3 tables
select
ORDERS.ORDER_NUM,
PRODUCT.PRODUCT_ID,
PRODUCT.PRODUCT_NAME,
ORDER_DETAILS.QUANTITY,
ORDER_DETAILS.UNIT_PRICE,
sum(ORDER_DETAILS.UNIT_PRICE) as SUBTOTAL
from
ORDER_DETAILS
inner join ORDERS on ORDER_DETAILS.ORDER_NUM = ORDERS.ORDER_NUM
inner join PRODUCT on ORDER_DETAILS.PRODUCT_ID = PRODUCT.PRODUCT_ID
group by
ORDER_DETAILS.ITEM_NUM
order by
PRODUCT.PRODUCT_NAME;
+-----------+------------+--------------+----------+------------+----------+
| ORDER_NUM | PRODUCT_ID | PRODUCT_NAME | QUANTITY | UNIT_PRICE | SUBTOTAL |
+-----------+------------+--------------+----------+------------+----------+
| 3004 | 2001 | BEER | 10 | 160,000 | 160 |
| 3012 | 2001 | BEER | 5 | 160,000 | 160 |
| 3002 | 2005 | CAKE | 5 | 50,000 | 50 |
| 3001 | 2004 | CIGARETTE | 2 | 25,000 | 25 |
| 3011 | 2004 | CIGARETTE | 5 | 25,000 | 25 |
| 3005 | 2007 | ICE CREAM | 50 | 10,000 | 10 |
| 3007 | 2010 | MILK | 3 | 45,000 | 45 |
| 3010 | 2010 | MILK | 7 | 12,000 | 12 |
| 3008 | 2008 | NOODLES | 1 | 5,000 | 5 |
| 3013 | 2006 | SODA | 50 | 12,000 | 12 |
| 3009 | 2002 | WINE | 1 | 200,000 | 200 |
| 3003 | 2002 | WINE | 2 | 200,000 | 200 |
| 3006 | 2002 | WINE | 1 | 200,000 | 200 |
+-----------+------------+--------------+----------+------------+----------+

Answer 1

You don't specify the database. However, you need to fix your query:
Details from the order and order line are not appropriate, if you are summarizing by product.
The SELECT and GROUP BY lists should be consistent.
The total you want is probably the price times the quantity.
So, the query should be more like this:
select p.PRODUCT_ID, p.PRODUCT_NAME,
sum(od.UNIT_PRICE * od.QUANTITY) as SUBTOTAL
from ORDER_DETAILS od join
ORDERS o
on od.ORDER_NUM = o.ORDER_NUM join
PRODUCT p
on od.PRODUCT_ID = p.PRODUCT_ID
group by p.PRODUCT_ID, p.PRODUCT_NAME
order by p.PRODUCT_NAME;
Also note the use of table aliases, so the query is easier to write and to read.