case calculation result is correct update table from a temp table

Question

I want to use CASE and see whether the columns = total then update a table with todays date.

UPDATE dbo.Audit 
       SET AUD_CloseDate =
       CASE
       WHEN Scored + NA = Total THEN GETDATE() 

At the end I want to see if col1 + col2 = col3, if so then update my column to todays date, and if there is a date already then do nothing.

Scored + NA = Total <---- they are from a temp table

Answer 1

You were almost ready:

UPDATE dbo.Audit 
SET AUD_CloseDate = CASE
                        WHEN Scored + NA = Total THEN GETDATE() 
                    END
WHERE AUD_CloseDate IS NULL

Answer 2

you need not run the update on all the rows, just filter on the ones where you want to update:

update dbo.audit
set    aud_closedate = getdate()
where  scored + na = total