Have you heard of functional encryption which allows a server to compute a function on encrypted data without knowing the decryption key and return the result in the clear. Therefore the server learns the result and nothing else about the encrypted data is leaked. There are possibility results but there is no practical, implementable scheme at present for general functions but there are schemes for specific functions like inner products (linear functions) and quadratics. With FHE, only the client, who has the decryption key, can learn the result so some interaction is needed for the server to learn the result. Each has their own applications.