求平均值用( )个聚合函数。
A. avg( )
B. max( )
C. average( )
D. mean( )
分组查询的关键字是( )
A. order by
B. from
C. group by
D. group
where子句、group by子句、having子句在select语句中的顺序是()
A. having子句、group by子句、where子句
B. group by子句、having子句、where子句
C. group by子句、where子句、having子句
D. where子句、group by子句、having子句
分组查询中,去掉不需要的组用( )关键字。
A. having
B. where
C. group by
D. from
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