LeetCode（数据库）- 只出现一次的最大数字

题目链接：​​点击打开链接​​

题目大意：略。

解题思路：略。

AC 代码

-- 解决方案(1)
WITH t1 AS(SELECT *
FROM my_numbers
GROUP BY num
HAVING COUNT(*) = 1
ORDER BY num DESC
LIMIT 1)

SELECT IF(COUNT(*) = 0, null, num) AS `num`
FROM t1

-- 解决方案(2)
SELECT
    MAX(num) AS num
FROM
    (SELECT
        num
    FROM
        number
    GROUP BY num
    HAVING COUNT(num) = 1) AS t
;