Select statement in SAP JCo

Dear Experts,

               I would like use Open SQL statements in SAP JCo. As of my knwoledge, my query will hit application server not the database, since it is an open SQL statement. So i need only SAP user credentials not database credentials. But i have seen in many examples they used database credentials.

      Is it neccessary to have database credentials to use Open SQL in SAP JCO?  If so will SAP client provide their DB credentials?

Please guide me. Thanks in advance.