题解 | #得分不小于平均分的最低分#

-- 找到SQL试卷得分不小于该类试卷平均得分的用户最低得分。
-- 1、关联过滤 2、计算平均值 3、最低得分，大于平均分，取最小的
SELECT 
    MIN(score)
FROM
    exam_record a
        INNER JOIN
    examination_info b ON a.exam_id = b.exam_id
WHERE
    tag = 'SQL' AND score IS NOT NULL
        AND score >= (SELECT 
            AVG(score)
        FROM
            exam_record a
                INNER JOIN
            examination_info b ON a.exam_id = b.exam_id
        WHERE
            tag = 'SQL' AND score IS NOT NULL);