I am uploading case through dataloader . But while mapping the fields from CSV to salesforce fields "Created by" field is not showing on the time of mapping from data loader on the time of Insert the case in salesforce and this field is already visible from the salesforce.
The CreatedBy Field is a read-only field that cannot be updated via dataloader without "Set Audit Fields upon Record Creation" permissions. Previously you had to file a Case with Support to turn this permission on for a limited period of time when importing data. Without the permission enabled you won't see it mapped when using dataloader.
You no longer need to file a case with Salesforce to give a user "Set Audit Fields upon Record Creation" permissions to allow the user to Set audit fields, such as Created By, Last Modified By, and Created Date when you create a record (API only i.e Importing Tools) with Data Loader in order to make the Created Date writable.
I have been trying this Feb. 2020. I confirm that the "Set Audit Fields upon Record Creation" permission set is required (or you can set it on custom profiles.) After turning off automated processes which updated the records after saving, I found that of the 4 audit fields only 3 could be set. The CreatedById could not be set and even when included manually in the mapping file, Data Loader would not map it.