Oracle_Sql语句执行速度慢

with tab as
(select o.*,c.id,c.reportseq,c.consultationresult,c.consultationdr, c.recorderid,c.recorder con_recorder,c.recorddt con_recorddt
from vieworderlist o
left join T_CONSULTATION c on o.orderseq =c.orderseq
where c.orderseq is not null)

select * from tab
where OrderDT>='2009-04-28 00:00:00' and OrderDT<='2009-10-29 23:59:59'
and ( MODALITY='CR' or MODALITY='CT' or MODALITY='US' or MODALITY='MR' or MODALITY='ES')
and ( PATTYPE='W' or PATTYPE='P' or PATTYPE='O' or PATTYPE='I')
要执行30秒，但是写成下边的则瞬间执行完成
with tab as
(select o.*, c.id,c.reportseq,c.consultationresult,c.consultationdr, c.recorderid,c.recorder con_recorder,
c.recorddt con_recorddt
from vieworderlist o
left join T_CONSULTATION c on o.orderseq =c.orderseq
where c.orderseq is not null)

select * from tab
where OrderDT>=

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