APEX

I am struggling with trying to implement a basic search that includes an optional date range for the data. The form looks the way I want it, but I can't seem to get the right syntax in the query. I can't get anything other than "no rows" to show up in the query if I implement a clause selecting records based on the time.

Here is a working query (without the time):

select m.AUDIT_ID, m.TIMESTAMP, m.LOC_ID, a.AREA, s.SUBAREA, d.OBSERVATIONS
from transys.SAFETY_AUDIT_MAIN m, transys.SAFETY_AUDIT_DETAIL d,
transys.SAFETY_AUDIT_AREA a, transys.SAFETY_AUDIT_SUBAREA s
where m.AUDIT_ID = d.AUDIT_ID (+)
and d.AREA_ID = a.AREA_ID
and d.SUBAREA_ID = s.SUBAREA_ID
and s.SUBAREA_ID NOT IN (198,199,398,399,498,499,798,799,898,899,999)
and (instr(upper(a.AREA),upper(nvl(:P210_SEARCH,AREA))) > 0
or instr(upper(s.SUBAREA),upper(nvl(:P210_SEARCH,SUBAREA))) > 0
or instr(upper(d.OBSERVATIONS),upper(nvl(:P210_SEARCH,OBSERVATIONS))) > 0)

I want to compare the m.TIMESTAMP column with page items P210_FROM_DATE and P210_TO_DATE.

I would also like to add in an optional filter comparing m.LOC_ID to P210_LOCATION, and I can't seem to figure out the "optional" part.

Any ideas would be helpful.