SQL: SUM on Aggregate columns - sql

Question

I have this query:
SELECT
spend_codes.spend_code,
SUM(orders.shipping_cost + orders.sales_tax + orders.manual_total + orders.fees) as order_total,
SUM(ordered_items.fees + ordered_items.price * ordered_items.quantity) as item_total
FROM spend_codeables
LEFT JOIN spend_codes
ON spend_codeables.spend_code_id = spend_codes.id
LEFT JOIN orders
ON spend_codeables.spend_codeable_id = orders.id AND spend_codeables.spend_codeable_type = 'App\Order'
LEFT JOIN ordered_items
ON spend_codeables.spend_codeable_id = ordered_items.id AND spend_codeables.spend_codeable_type = 'App\OrderedItem'
GROUP BY
spend_codes.spend_code;
Which has this result:
+--------------+---------------+--------------+
| spend_code | order_total | item_total |
|--------------+---------------+--------------|
| 1230131391 | $362.00 | <null> |
| A12345 | <null> | <null> |
| B29393 | <null> | $374.28 |
+--------------+---------------+--------------+
However, I'd like to add order_total and item_total in order to get just total.
So I'd expect this:
+--------------+---------------+
| spend_code | total |
|--------------+---------------+
| 1230131391 | $362.00 |
| A12345 | <null> |
| B29393 | $374.28 |
+--------------+---------------+
Doing this did not work:
SUM(orders.shipping_cost + orders.sales_tax + orders.manual_total + orders.fees) +
SUM(ordered_items.fees + ordered_items.price * ordered_items.quantity) as total
Another monkeywrench is that the type of the numbers is money not integer.
Anyone would be able to help?

Answer 1

If any of the 2 sums returns NULL then the result of the sum of the sums will also be NULL because NULL + anything returns NULL.
Use SUM() only once:
SUM(
orders.shipping_cost +
orders.sales_tax +
orders.manual_total +
orders.fees +
ordered_items.fees +
ordered_items.price * ordered_items.quantity
) as total
If any of the columns involved may also be NULL use COALESCE() like COALESCE(orders.shipping_cost, 0::money)

Answer 2

you do it in next step using sub query and I used coalesce() for avoid null
with cte as ( SELECT
spend_codes.spend_code,
SUM(orders.shipping_cost + orders.sales_tax + orders.manual_total + orders.fees) as order_total,
SUM(ordered_items.fees + ordered_items.price * ordered_items.quantity) as item_total
FROM spend_codeables
LEFT JOIN spend_codes
ON spend_codeables.spend_code_id = spend_codes.id
LEFT JOIN orders
ON spend_codeables.spend_codeable_id = orders.id AND spend_codeables.spend_codeable_type = 'App\Order'
LEFT JOIN ordered_items
ON spend_codeables.spend_codeable_id = ordered_items.id AND spend_codeables.spend_codeable_type = 'App\OrderedItem'
GROUP BY
spend_codes.spend_code
) select spend_code,coalesce(order_total,0)+coalesce(item_total,0) as total from cte