Deriving attribute Currency using Char relationship

I have a scenario of deriving attribute from Company code using Char relationship and query is input ready only if I place Currency in rows/columns pane of the query. In case if I remove Currency from query, cells are not input ready for the query.

Company code and Currency is included in aggregation level and in real time info cube.

Could you please let me know why we need to place Currency in query when we are deriving the attribute using Char relationship ?

Thanks in advance..

Edited by: peppy on May 16, 2011 11:47 AM