Use a variable in query

I've got oracle database and KNIME 3 and I need to use variable in a query to filter data according to date but i see there is a lack of types of variables in workflow variables type list (no date type). Moreover KNIME converts my string variable "Report_date" (it equals to "2013-10-03") in a query to duoble ot integer so this query

select '2013-10-03', $${SReport_date}$$ ddd from dual

returns this 

2013-10-03    2001.0.

How do one can do a filtering by date using KNIME variables?

Thank you KNIMErs for your pasionate help. The answer is

select '2013-10-03', '$${SReport_date}$$' ddd from dual


You are welcome.