MySQL Set the phone field to be the only one after inserting a record that is the same as a recording of a cell phone number. SQL statement error instead of returning insert Error! What to do

MySQL Set the phone field to be the only one after inserting a record that is the same as a recording of a cell phone number. SQL statement error instead of returning insert Error! What to do

$User=M('User');        $result=$User->add($data);           if($result){          $da['code']='1';          $da['message']="注册成功";          $da['token']=$data['token'];               echo json_encode($da);           }else{          $da['code']='0';          $da['message']="手机已注册";          $da['token']="null";               echo json_encode($da);           }```

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