some questions about rdb (vms system)

Hello,
I used to develop in Oracle and Sql-Server.

I need good help file for RDB (VMS system)

Also,
What is the equivalent in RDB (VMS) for :
select an_expression from dual; ?

I need help for all the functions in RDB, please.
i.e how can I left pad a string with 10 leading spaces ?

Thanks :