It's not clear what you're asking, I think somewhat from the language barrier.
So , as you are saying that I should not provide the key to other user, whom I don't want to see that clear text column..How I can do that.?
what key, and regardless, what does the key have to do with the clear text column? It would help if you laid this out in a scenario with a real table, and what you want people to see or not see. Right now I think you don't understand encryption and how it's used, and that makes it hard to discuss.
There is no "have". Users who log into the server can see and access various objects. In the case of encryption, you have another key, or a password protecting that key. Without that password, accessing the key doesn't matter.
As far as a good practice, it's never a good practice to have encrypted data and encrypted data on the same system. It defeats the purpose of using encryption.
The retrofit of encryption into an existing application is complex and requires lots of work. Encryption also should be used sparingly.