The first error ID is for when a user name already exists in the system.

第一个错误 ID 是用于系统中已经存在一个用户名的情况。

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With this design, a user who encounters an error such as a duplicate user ID will be returned to the form and will only have to change the user ID, rather than reenter the entire form.

使用这种设计，遇到错误(比如重复的用户标识)的用户将回到表单，且只须更改用户标识，而不必重新输入整个表单。

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Now, when an error is returned, you check for the error ID rather than simply displaying a default error message that isn't helpful to the user.

现在，如果返回一个错误，您就可以检查错误ID，而不只是显示对用户没有帮助的默认错误消息。

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