Encrypt data to hide them to web hosting provider

I have a web application in which registered users enter data in a few forms and then, when they log in at a later stage, they see forms populated with their data. Data is stored on Postgresql server of the same hosting provider of the web server.

I'd like to encrypted data stored on Postgresql to prevent them to be read by the hosting provider.

I don't think this is possible to do, because whenever is the encryption key kept, if the webserver has to access it in order to serve pages to users, then it can use it to decrypt data to read them. Anyway I preferred to ask just to be sure I'm not missing something.