How to remove a trailing comma at the end of a string in Oracle

So I'm working in a database and in a particular column there is a trailing comma that I need to remove, a simple solution is something like this: We have something like this

SELECT 'a, b, c, d,' test From  dual;

The output is:

a, b, c, d,

To clean the last comma we can use RTRIM

SELECT RTRIM('a, b, c, d,', ',') new_test From  dual;

The output is:

a, b, c, d

Pretty neat!!!! RTRIM function Source 2

Trying to connect to oracle with Pentaho Ketlle and failed

So I was trying to connect to a Oracle database when I got this error

Connection failed. Verify all connection parameters and confirm that the appropriate driver is installed.
Listener refused the connection with the following error:
ORA-12505, TNS:listener does not currently know of SID given in connect descriptor
 

The configuration for the connection that I have is using the "Service Name" so in this case is an easy fix, just put a "/" in the beginning , like this.