How to add a second autoincrement and populate the field?

Question

MySQL

There is a completed table. You need to add a field that will be an auto-increment. This field is the second autoincrement in the table and is not a primary key. How (when|after) adding a field to overwrite all the data in the table, and assign the initial value of the field, for example, 100?

Answer 1

ALTER TABLE `sometable` 
ADD COLUMN `id` INT AUTO_INCREMENT PRIMARY KEY,
AUTO_INCREMENT=100;

or create default then update id to id + 99