Something like this.
Warning: My syntax may not be entirely correct
Update salespersons set salary = salary * 1.12 where salespersons.empid =
(SELECT employeeid
FROM (SELECT *
FROM (SELECT *
FROM (SELECT s.empid employeeid,
s.ename employeename,
SUM(i.price * oi.qty) - s.salary Topprofit
FROM salespersons s
LEFT JOIN orders o ON s.empid = o.empid
LEFT JOIN orderitems oi ON o.orderid = oi.orderid
LEFT JOIN inventory i ON oi.partid = i.partid
GROUP BY s.empid, s.ename, s.salary)
ORDER BY Topprofit DESC)
WHERE ROWNUM = 2
ORDER BY Topprofit ASC)
WHERE ROWNUM = 1 and Topprofit is not null);