In Oracle, if you want to generate the days between two date, use :

select to_char (to_date('2011-01-01','YYYY-MM-DD')   + rownum -1, 'YYYY-MM-DD')  from all_objects 
where 
rownum <= to_date('2011-01-31','YYYY-MM-DD') - to_date('2011-01-01','YYYY-MM-DD') + 1

the ouput is:
2011-01-01
2011-01-02
2011-01-03
................
................
2011-01-31