题解 | 找出每个学校GPA最低的同学

SELECT
    device_id,
    university,
    gpa
FROM
    (
        SELECT
            device_id,
            university,
            gpa,
			-- 窗口函数，根据university分组，并按照gpa排序
            ROW_NUMBER() OVER (
                PARTITION BY
                    university
                ORDER BY
                    gpa
            ) AS rn
        FROM
            user_profile
    ) t
WHERE
 	-- 只取每个分组的第一条
    rn = 1;