For user creation/updating, you can use as many CSV files as you'd like. The key is in the unique identifier. If your files duplicate unique identifiers, data will be overridden.
For example, if my first file contains information for the following unique identifiers:
The first file will add Billy, Sally, and Thor to my user list. The second file upload will add Randy and William, but overwrite anything from the first file for Thor. If the information in both files is the same for Thor, then it doesn't matter, but if the information is different (or for two different people), the information for the second upload of Thor will overwrite (and more or less wipe out) the first Thor's information.
So, the number of CSV files doesn't matter. It only matters that you pay attention to duplicate unique identifiers so you don't accidentally overwrite someone's data unintentionally.
For user creation/updating, you can use as many CSV files as you'd like. The key is in the unique identifier. If your files duplicate unique identifiers, data will be overridden.
For example, if my first file contains information for the following unique identifiers:
billy@company.com
sally@company.com
thor@company.com
And my second file contains information for the following unique identifiers:
randy@company.com
william@company.com
thor@company.com
The first file will add Billy, Sally, and Thor to my user list. The second file upload will add Randy and William, but overwrite anything from the first file for Thor. If the information in both files is the same for Thor, then it doesn't matter, but if the information is different (or for two different people), the information for the second upload of Thor will overwrite (and more or less wipe out) the first Thor's information.
So, the number of CSV files doesn't matter. It only matters that you pay attention to duplicate unique identifiers so you don't accidentally overwrite someone's data unintentionally.