enrollment number should not be null

Summary:

Description:I have loaded learning record for one learner by using hdl. For learning Record Number column i had given value as null[system is not allowing to load with blank] after data loaded successfully i have checked in the front end enrollment number is showing as null

I had tried by giving random number for LearningRecordNumber but system is throwing an error. I need to get some number in the UI under enrollment. kindly assist me on this

I need lookup codes for loading learning records for different use cases. Kindly share me the document links if anyone have.