Validation issues with thinkphp

thinkphp Validation related issues
In the login and registration needs to verify the user name, but in the login to verify that the user name is empty, the user name exists;
But you also need to verify when registering, are the two validations the same? Sos
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Different, you can control the parameters to ensure that each validation is for which action
Http://doc.thinkphp.cn/manual/auto_validate.html
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The process of proving is the same.

But there's a difference.
Login, the user name cannot be empty, and exists, in order to pass through

When registering, the username cannot be empty and does not exist to pass through (the same user name cannot be re-registered)
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Two methods of verification are the same

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, the validation is null with JS judgment, verify that there is a need to query the database, and then judge

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