I'm probably wrong but:
I think it may be related to an enhancement request made to sybase to know the aliased table.columname - the real actual table name and column name for the datawindow column, as well as the names used in the select.
for example:
select table1.col1 A, table2.col1 B
from table table1
join table table2 on table1.joinid = table2.otherid
the dbname in the datawindow would reference the alias which is not the actual column/table name.
If you want to get the real table name/column name there would be no way to get it outside of parsing the sql. i believe that the dbalias was an attempt to provide that information? (it never worked correctly.)
in any case, the ideal would be to have the table1_A as dw field name (or #1), and use that to get things such as the table alias (table1), the real table (table), the aliased column name (A), and the real column name (col1)