пара фирменных решений
SELECT TOP 1 [WITH ties] Name, Salary
FROM employee
ORDER BY Salary DESC
SELECT Name, Salary
FROM employee
ORDER BY Salary DESC
LIMIT 1
и стандартное
WITH E AS
(
SELECT Name, Salary,
ROW_NUMBER() OVER (ORDER BY Salary DESC) RN /*Or RANK() for ties*/
FROM employee
)
SELECT Name, Salary FROM E WHERE RN=1