Comment by dandraper

Because queries are encrypted, too. And you need to be authorized to encrypt a query term. That's the whole crux.

TBH, I'm so close to this now I forget that part isn't obvious! You literally can't do:

select * from blah where secret_col == 10

And get meaningful results. You can only do something like:

select * from blah where secret_col == Encrypt(10);

And in order to generate that encrypted query, you must be authorized. So an adversary can't simply do trial and error queries to guess records.