How Code Attributes works in MDS stage in MDM model

Hi,

Can i have a combination of sources some with Unique Identifiers and some without?

I need to knowwhat happens when I have option “Create Code values automatically” selected for the entity and same time
pulling Unique Identifier for other sources in same entity stage table.

When we select option “Create Code values automatically” for the entity we creates, then during load from external source to MDM stage we don’t send any values to MDM stage “Code” field and in next step when we execute the stored procedure to load the data from MDM stage to MDM model, it assigns the Code values to each record in MDM stage and MDM model.

I need to know whether after executing the store procedure, will it assign Code values for only NULL records in MDM stage and not give us any error for the records that already have Code values present in MDM stage.

Please suggest the good approach.

Thanks,

Akash