【多选题】
A select (name) from table person: 所有记录的name字段的值
B select (name) from person where age=12 or name="aa"; or 或者
C select (name) from table person where age=12; 查找age=12的记录的那个字段的值
D select (name,age) from person where age=12 and name="aa"; and 并且
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