怎么把这两条SQL语句合并
select * from bsj where (mc_time = '2010-09-15' and ref_xdc < 0 )
and
select * from bsj where (mc_time = '2010-09-16' and ref_xdc < 0 )
select * from bsj where (mc_time = '2010-09-15' and ref_xdc < 0 )
and
select * from bsj where (mc_time = '2010-09-16' and ref_xdc < 0 )
where mc_time in('2010-09-15','2010-09-16') and ref_xdc<0