The foreign key side is also denoted by a key symbol.

外键方也由键符号表示。

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The primary key side of a one-to-one relationship is denoted by a key symbol.

一对一关系的主键方由键符号表示。

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A primary key column is identified by a primary key symbol in its row selector.

主键列由其行选择器中的主键符号标识。

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And most of these commands you don't actually need but this little caret symbol means control, so every keyboard these days has a control key so you hold that and hit X for instance to exit the program.

这里大多数命令你们都用不着,这个小插入符意味着控制，每个键盘都有一个控制键,譬如，当你敲入X时，就退出这个程序。

哈佛公开课 - 计算机科学课程节选

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