Re-formatting your statement so braces are aligned:
Select * From A
AND
(
(
'1-Nov-2010' between OM_MERCH_CUST.MC_FM_DT AND coalesce
(
OM_MERCH_CUST.MC_TO_DT,sysdate
(
)
)
)
OR
(
'30-Nov-2010' between OM_MERCH_CUST.MC_FM_DT AND coalesce
(
OM_MERCH_CUST.MC_TO_DT,sysdate
(
)
)
)
);
You have the right number of braces, but did you mean to have the OR clause within the AND?