문제
정답
SELECT () AS ~
를 쓰면 NULL값을 보존할 수 있다.
SELECT (
SELECT salary
FROM employee
GROUP BY salary
ORDER BY salary DESC
LIMIT 1
OFFSET 1) AS SecondHighestSalary
SELECT () AS ~
를 쓰면 NULL값을 보존할 수 있다.
SELECT (
SELECT salary
FROM employee
GROUP BY salary
ORDER BY salary DESC
LIMIT 1
OFFSET 1) AS SecondHighestSalary