Failed to upgrade from Atlassian-Confluence -6.14.0 to Atlassian-Confluence -7.0.5

[vajraboy]

On Atlassian Confluence was - 6.14.0 backup, then Atlassian Confluence was - 7.0.5 to restore an error:

 com.atlassian.confluence.importexport.ImportExportException: Unable to complete import because the data does not match the constraints in the Confluence schema. Cause: MySQLIntegrityConstraintViolationException: Duplicate entry '' for key 'unq_lwr_username'

[Robert Wen_Cprime_ · Accepted solution]

You may want to check out the following Knowledgebase article: https://confluence.atlassian.com/confkb/restore-of-a-site-xml-backup-fails-due-to-duplicate-entry-for-key-unq_lwr_username-error-998896818.html