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select
a.*,b.*,c.leiming
from
Bookinfo a
left join
chubanshe b on a.chubansheID=b.ID
left join
class c on c.ID=a.classID--这里定义列
select
a.*,b.*,c.leiming
from
Bookinfo a
left join
chubanshe b on a.chubansheID=b.ID
left join
class c on c.ID=b.ID