Design a table relationship?

Question

Database design

There is this table:

CREATE TABLE `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `nickname` varchar(30) DEFAULT NULL,
  `email` varchar(30) DEFAULT NULL,
  `password` varchar(32) DEFAULT NULL,
  `reg_date` datetime DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  UNIQUE KEY `nickname` (`nickname`)
)

Another one is required, it must also contain users and other data, so is it better to take the id or nickname field?

Answer 1

ID
UNIQUE KEY `nickname` (`nickname`)and `nickname` varchar(30) DEFAULT NULLmeans that there can be only one user without a nickname.

Answer 2

Firstly, use an ID
; secondly, expand the mail field to 256 characters, make a unique index on it

Answer 3

so what is better to take the id or nickname field?

Take as a reference field of a foreign key of another table? In some DBMS, for example, in MySQL, it is not possible to assign a foreign key to a non-primary key (of another table).