Sorry, I can’t answer your questions. I know ______ about the subject.
A. a little
B. little
C. few
D. a few
查看答案
They received of letters about their TV programs.
A. dozen
B. dozen and dozen
C. score
D. dozens
How many birds can you see in the trees？-- I can see birds in them.
A. hundreds of
B. five hundreds
C. hundred of
D. five hundreds of
以下关于索引描述中,错误的是( )。
A. 一个基本表可以创建多个索引
B. 索引可以提高数据查询的速度
C. 删除索引可以使用DROP INDEX语句
D. 索引越多越好
为teacher表的tel列创建一个唯一索引un_tel, 下列SQL语句写法是正确的是( )。
A. CREATE TABLE teacher ADD UNIQUE INDEX un_tel(tel)
B. CREATE INDEX teacher ADD UNIQUE INDEX un_tel(tel)
C. ALTER TABLE teacher ADD UNIQUE INDEX un_tel(tel)
D. ALTER TABLE teacher MODIFY UNIQUE INDEX un_tel(tel)
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