SQL多表联合查询（LEFT JOIN）条件差异

Posted 2020-09-21 一个人上路

查询A：

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

查询B：

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

查询A、B的结果差异：

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

 

查询A中只有两表互相之间能关联的结果；

查询B中还包含未与b关联的结果，因此记录数比查询A多；