Then again, what if the auditor was from a government agency? It might not be so easy to tell a government agency what tables they can and cannot look at...
That is a main purpose for table views, which allow the user to see some data (columns) in a table, while others are not viewable. Email and password hash would seem to be excellent candidates for exclusion to an auditor.
You can set up SQL to only grant access to specific tables based on their username/password combination. You can also further restrict access by IP address -- which, as I understand, was in place.
So, for example, you could have complete access for Bob, and only show the user# and email addresses to Bill. And you can set it up so that Bob can only log in from his own IP address, while Bill can log in from any IP address.
So if the auditor was only supposed to be auditing for evidence of gaming/fraud, then the auditor account access should have only been permitted to read those tables specific to what they were looking for.
Either the story as given to us so far is false,
or the admin of the SQL database gave too much access/permission to the auditor's SQL account. If too much access was given, then that MIGHT rise to the level of negligence, or even gross negligence.