自动生成主键和未知的主键。

Automatic primary key and unknown primary key generation.

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主键列由其行选择器中的主键符号标识。

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

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表通常包括一个主键，该主键确保每个行都是唯一的。

A table usually includes a primary key that ensures every row is unique.

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表通常包括一个主键，该主键确保每个行都是唯一的。

A table usually includes a primary key that ensures every row is unique.

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