My question is quite related to the concept of homomorphic encryption, which is not practical at all nowadays.
In short, I would like to know how to query encrypted databases. Simple queries which test the equivalence of the entries can be easily implemented. Fine.
How about queries like: "select all employees with salary greater than 10000"?
The naive approach would be to select all employee id's along with their corresponding salary, decrypt everything and then check which ones match the aforementioned condition. Obviously this is far from being efficient.
Is there a more efficient way to handle such queries into encrypted data? Maybe some partially homomorphic algorithm?
My background: I have been in the academia for a while, so I know quite a lot about the concepts, but have no idea how these concepts have been employed by the industry so far.