Joins in the report studio

[Redi]

I have a report studio report with two queries, Query1 and Query2. I am joining the two queries to form Query3 on the common key say ColumnA in the query explorer (Query1.ColumnA=Query2.ColumnA) using the join option in the toolbar to develop a list report from the Query3. the report is validated and when i run this report or even try to get the tabular data i dont get any results. but the cognos generated SQL runs fine and gives back the results when i run it in database.
The ColumnA is a character data type in Teradata database (has only numeric data in the column for now). I changed the column usage from identifier to attribute in FM and tried to run the report it did not work.
Now when i changed the joined condition in report studio to
to_number(Query1.ColumnA)= to_number(Query2.ColumnA) it gave me back the results and the cognos generated SQL was same as before expect for the to)number change in the join condition.
Any one has any idea why this is happening?
I want to find a solution as there is a chance that the column might have alpha-numeric data.