题解 | 得分不小于平均分的最低分

SELECT MIN(er.score) AS min_score_over_avg

FROM exam_record AS er

LEFT OUTER JOIN examination_info AS ei

ON er.exam_id = ei.exam_id

WHERE ei.tag = 'SQL' AND er.score >= (SELECT AVG(er.score) AS avg_score # 方法一：表联结

FROM exam_record AS er

LEFT OUTER JOIN examination_info AS ei

ON er.exam_id = ei.exam_id

WHERE ei.tag = 'SQL');

# 找出SQL试卷平均分数的方法二: IN查询

SELECT AVG(er.score) AS avg_score

FROM exam_record AS er

WHERE er.exam_id IN(

                    SELECT ei.exam_id

                    FROM examination_info AS ei

                    WHERE ei.tag = 'SQL'

)