select a.id,a.name as teamA的name,b.name as teamB的name,c.name asleague的name from 表A a inner join 表team b on a.id=b.id inner join 表league c on a.id=c.id
select A.id,teamA.name,league.name from A a left join teamA b on a.teamA_id=b.id left join league c on a.league_id=c.id
select aa.id ,[teamA的name]=a.name ,[teamB的name]=b.name ,[league的name]=c.name from A aa left join team a on aa.teamA_id=a.id left join team b on aa.teamB_id=b.id left join league c on aa.league_id=c.id
select a.id,a.name teamA的name,b.name teamB的name,c.name league的name from 表A a inner hash join 表team b on a.id=b.id inner hash join 表league c on b.id=c.id 根据具体情况,来执行内,外连接. 外连接的查询性能要低于内联接的查询性能. 上面用的是hash连接,您最好自己进行测试,看一看哪一种的查询效率最高,然后就选择哪一种.
from 表A a
inner join 表team b
on a.id=b.id
inner join 表league c
on a.id=c.id
left join teamA b on a.teamA_id=b.id
left join league c on a.league_id=c.id
,[teamA的name]=a.name
,[teamB的name]=b.name
,[league的name]=c.name
from A aa
left join team a on aa.teamA_id=a.id
left join team b on aa.teamB_id=b.id
left join league c on aa.league_id=c.id
from 表A a
inner hash join 表team b
on a.id=b.id
inner hash join 表league c
on b.id=c.id
根据具体情况,来执行内,外连接.
外连接的查询性能要低于内联接的查询性能.
上面用的是hash连接,您最好自己进行测试,看一看哪一种的查询效率最高,然后就选择哪一种.