一个查询语句执行后显示的结果为
1班 80
2班 75
3班 NULL
则最有可能的查询语句是
SELECT AVG(成绩) FROM 成绩表 WHERE class<=3
SELECT AVG(成绩) FROM 成绩表 WHERE class<=3 GROUP BY class
SELECT AVG(成绩) FROM 成绩表 WHERE class<=3 order by class
SELECT AVG(成绩) FROM 成绩表 HAVING class <=3 GROUP BY class