SQL returns wrong value (?) - sql

Question

SQL Case statement with formula returns the wrong value in the column. What I am trying to do is to calculate the absolute value based on several conditions. First of all when the risk_class is either "Not enough samples" or "Regular price" the absolute value should be zero. Secondly, when the difference between the mode and the price is less than zero, the absolute value should be zero. If all these conditions are not met, then the risk_abs should be the difference between the mode and price multiplied by the quantity column corresponding with the row.
UPDATE dbo.import_company
SET risk_abs = ROUND(t.risk_abs, 0)
FROM (
SELECT invoice_ref, risk_class, modus, price, quantity,
CASE
WHEN risk_class = 'Onvoldoende observaties' THEN 0
WHEN risk_class = 'Gefactureerd tegen reguliere prijs' THEN 0
WHEN (modus - price) < 0 THEN 0
ELSE (modus - price) * quantity
END AS risk_abs
FROM dbo.import_company
)
t WHERE t.invoice_ref = dbo.import_company.invoice_ref
SELECT invoice_ref, article_code, quantity, price, modus, risk_class, risk_abs
FROM dbo.import_company
WHERE risk_class = 'Gefactureerd tegen reguliere prijs'
I don't understand why me result is different, and the formulas don't work. See below
I don't get how the 140 is calculated and why it ignores all statements?
Any advice and tips on what I am doing wrong are welcome!

Answer 1

There's no aggregation here or any other reason I can see to use a subquery to do the CASE logic. So we can get rid of that and the too-loose attempt at correlation between the subquery and the table:
UPDATE dbo.import_company
SET risk_abs = ROUND(CASE
WHEN risk_class = 'Onvoldoende observaties' THEN 0
WHEN risk_class = 'Gefactureerd tegen reguliere prijs' THEN 0
WHEN (modus - price) < 0 THEN 0
ELSE (modus - price) * quantity
END, 0)