A. = B. in C. like D. <>
A. 选择全部元组 B. 选择全部字段 C. 选择主码所在列 D. 选择有非空约束的字段
A. * B. % C. - D. ?
A. order by B. where C. group by D. having
A. top B. percent C. distinct D. having
A. where B. order by C. group by D. 无须配合
A. age is null B. age is not null C. age = null D. ifnull(age)
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
A. SUM B. ABS COUNT D. AVG
A. asc B. between C. in D. desc
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