>>The default value in the column generates a constraint. So, it's not WITH VALUES that is problematic. The DEFAULT value should produce a constraint (unless it was created with now deprecated syntax of bind default).
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>Yes, but WITH VALUES cannot be used alone as it wouldn't know which value to store in the existing records. Isn't it what DEFAULT was also used for in the way I had it? While DEFAULT can be used alone, I am not sure WITH VALUES can be used as is.

Why you don't want to keep the field NULL ?