GENERATED BY ALWAYS AS IDENTITY和GENERATED BY DEFAULT AS IDENTITY的区别

本文主要是介绍GENERATED BY ALWAYS AS IDENTITY和GENERATED BY DEFAULT AS IDENTITY的区别，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

identity是定義自動加一的列，就像個自動編號。sqlserver裡也有。
這個值有個特點就是不會重複，所以你叫它自動生成的唯一值也可以。
GENERATED BY ALWAYS AS IDENTITY
GENERATED BY DEFAULT AS IDENTITY

By always和by default是說明生成這個IDENTITY的方式。

By  always是完全由系統自動生成。
by default是可以由用戶來指定一個值。

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