函数依赖范围内的最高范式级别为( )（2.6）
A. 3NF
B. 4NF
C. 5NF
D. BCNF
查询student表中的所有非空email信息, 以下语句正确的是( )。（2.6）
A. Select email from student where email !=null
B. Select email from student where email not is null
C. Select email from student where email <> null
D. Select email from student where email is not null
现有书目表book,包含字段:价格price (float),类别type(char); 现在查询各个类别的平均价格、类别名称,以下语句正确的是( )。（2.6）
A. select avg(price),type from book group by type
B. select count(price),type from book group by price
C. select avg(price),type from book group by price
D. select count (price),type from book group by type
现有表book,字段:id (int),title (varchar), price (float); 其中id字段设为主键, 使用insert语句向book表中插入数据,以下语句错误的是( )。
A. insert into book ( title, price) values('java',100)
B. insert into book values(1，'java',100)
C. insert into book ( id, title) values (1,'java')
D. insert into book (id,title,price) values(1,'java',100)
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