SQL多表聯合查詢（LEFT JOIN）條件差異

查詢A：

select a.*,b.* into Bus605115_ON_Where_And --(642 行受影響)
from PositionN a left join szt b
on b.[fQCBH]=a.fBusNo
where fdealtime between fDInTime and fDInTimeN
and fbusno=605115

查詢B：

select a.*,b.* into Bus605115_ON_And_Where --(835 行受影響)
from PositionN a left join szt b
on b.[fQCBH]=a.fBusNo
and fdealtime between fDInTime and fDInTimeN
where fbusno=605115

查詢A、B的結果差異：

select * from Bus605115_ON_And_Where a
where not exists
(
select 1 from Bus605115_ON_Where_And b
where a.fGuid=b.fGuid
)
order by a.fDInTime

 

查詢A中只有兩表互相之間能關聯的結果；

查詢B中還包含未與b關聯的結果，因此記錄數比查詢A多；