Would this SQL line work?

Hi there,

I have imported some products with some incorrect stock status, would this SQL work?

UPDATE `itmeup_product`
SET stock_status_id = CASE
WHEN quantity=0 THEN 5*stock_status_id
ELSE stock_status_if
END

If Quantity is = then set Stock Status 5 = (Out of Stock)
Currently its is showing as 6 (2-3 Days)

Why dont' use something like this?
or etc...

Is weird to ask for 20 years experience in IT