... ON [сотрудники].[Salary] >= [уровни зарплат].[Losal] AND [сотрудники].[Salary] <= [уровни зарплат].[Hisal]
SELECT e.Name, e.Salary, max(s.Hisal) Hisal FROM EMP e JOIN SALGRADE s ON e.Salary between s.Losal and s.Hisal GROUP BY e.Name, e.Salary