How to update two records with two different values with two 'where' conditions at once?
UPDATE account
    SET balance = balance +  CASE WHEN accountID = 1 THEN amount 
                                               WHEN accountID = 2 THEN amount * -1
                                               ELSE 0
                                               END
WHERE accountID IN (1,2)


The * is the multiply operator, that means amount * -1 = - amount - dat-nguyen