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
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
