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'
)
