I've done a little research on this in the past hour, and I could use some help understanding some things.
Why doesn't this work? Got the basis for it from link
ALTER TABLE customers
MODIFY COLUMN customer_id INT AUTO_INCREMENT PRIMARY KEY;
When I attempt to run it, I receive the error: Multiple primary key defined.
It works when I take out PRIMARY KEY, but is it still doing what I need it to do? (which is increment the customer_id, which is a PK, by 1.)
The customer_id is a primary key, does marking it as a primary key make it think that there are two?
Another question, when you use AUTO_INCREMENT without declaring how many it increments by, what is the default value to increment, 1?