SELECT查询中,要把查询结果按照某一列的值进行排序,所用到的子句是()
A. order by
B. where
C. group by
D. having
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在select语句中,用于去除重复行的关键字是()
A. top
B. percent
C. distinct
D. having
select语句中,通常与having子句同时使用的是()子句
A. where
B. order by
C. group by
D. 无须配合
MySQL中,下列涉及空值的操作,不正确的是()
A. age is null
B. age is not null
C. age = null
D. ifnull(age)
假设数据表“职工”表中有10条记录,获得“职工”表最前面两行记录的命令为()
A. select 2 * from 职工
B. select * from 职工 limit 2
C. select percent 2 * from职工
D. select 2 from职工