将student表按照gender字段进行分组查询,查询出grade字段值之和小于300的分组,依据上述要求,下面选项中,正确的SQL语句是

从student表中查询学生姓名、年龄和成绩，结果按照年龄降序排序，年龄相同的按照成绩升序排序，下面SQL语句正确的是： A: select name, age, score from student order by age desc , score; B: select name, age, score from student order by age , score asc; C: select name, age, score from student order by 2 desc , 3 asc; D: select name, age, score from student order by 1 desc , 2；

下面用if语句统计“成绩(score)优秀的男生以及不及格的男生”的人数，正确的语句为_____。 A: if(gender=="男" and score <60 or score>=90): n+ = 1 B: if(gender=="男" and score <60 and score>=90): n+ = 1 C: if(gender=="男" and (score <60 or score>=90)): n+ = 1 D: if(gender=="男" or score <60 or score>=90): n+ = 1

要从SC表中查找缺成绩（SCORE）的学生学号（NO），相应的SQL语句是（ ）。 A: SELECT NO FROM SC WHERE SCORE = 0 B: SELECT NO FROM SC WHERE SCORE IS 'NULL' C: SELECT NO FROM SC WHERE SCORE = NULL D: SELECT NO FROM SC WHERE SCORE IS NULL

下列的查询语句哪一项是错误的（选一项） A: Select * from stumarks where score>=60 B: Select * from (select * from stumarks where score>=60) C: Select * from (select * from stumarks where score>=60) as temp D: Select * from (select * from stumarks ) as temp where score>=60