How do I update the User Distinguished Name?

I am working on building a report that references the PER_USERS table in our ERP environment? However, I have noticed that the USER_DISTINGUISHED_NAME column has inconsistent data. Sometimes the field includes the first and last name of the users as part of the string, while other times it only seems to have random numbers/letters populated in the field. I was hoping to somehow update it to consistently have the first and last name as part of the field.