A primary key is a constraint that assures that each table contains no duplicate rows.

主键是确保每个表都不包含重复行的约束.

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Explains how to filter duplicate rows out of Select queries.

解释如何从“选择”查询中筛选出重复的行.

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Respectively, be achieved using arrays and linked the file to remove duplicate rows.

分别用数组和链表方式实现去除文件中的重复行.

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