JDBC Adapter: SELECT statement with substring

Hi,

I use the JDBC Sender Adapter for getting data out of an oracle database and I my select out of an nonSAP system looks like this:

database:

hkey hdatajhz hdatam hdatat

1300234 2005 05 01

select XXXXX from <database>

where

hdatajhz||hdatam||hdatat = '20050501'

and substr(hkey,3,2) = '00'

Both statements doesent't work, why??

Regards

Christoph