A primary key is a special thing in the relational model: It must be unique to each record (row) of a table.

在关系模型中主键是特殊的事物：它对于表的每个记录(行)必须是唯一的。

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A primary key is a special thing in the relational model: It must be unique to each record (row) of a table.

在关系模型中主键是特殊的事物：它对于表的每个记录(行)必须是唯一的。

youdao