MySQL - how to use VARCHAR as AUTO INCREMENT Primary Key

Question

I am using a VARCHAR as my primary key. I want to auto increment it (base 62, lower/upper case, numbers), However, the below code fails (for obvious reasons):

Answer 1

Or just create a sequence and maintain the pk field using the sequence to generate the primary key value with nextval function. And if perf is an issue, use cache on sequence.

But as others have stated, this is sub-optimal, if your primary key contains a numbered sequence then it's better to use int and auto-increment. I don't see a use case where pk has to auto-increment but be a varchar data type, it doesn't make sense.