SELECT学号,姓名,平均成绩FROM S,SC; WHERE 学号=S学号; GROUP BY 学号HAVING COUNT(*)>=5 ORDER BY平均成绩DESC SELECT学号,姓名,AVG(成绩)FROMS,SC; WHERE 学号=S学号AND COUNT(*)>=5; GROUP BY学号ORDER BY 3 DESC SELECT学号,姓名,AVG(成绩)平均成绩FROM S,SC; WHERE 学号;S学号AND COUNT(*)>=5; GROUP BY 学号ORDER BY平均成绩DESC SELECT学号,姓名,AVG(成绩)平均成绩FROMS,SC, WHERE 学号:S学号; GROUP BY学号HAVING COUNT(*)7=5 ORDER BY 3 DESC