Database links are created between databases. In my case, the schema reside the same database and I own both the schema.
workspace: a, schema: a (default)
workspace: b, schema: b (default)
Login to workspace b -> SQL Workshop :
grant select on b.table to aDB;
Login to workspace a -> SQL Workshop :
select * from b.table;
the precondtion is that you need have grant privligle on workspace b.