namount intselect sum(c.namount) as total from base_product c left outer join prod_incoming a on a.cname=c.cname and left outer join prod_outgoing b on b.cname=c.cname 怎么三个表连接就出问题?
select sum(c.namount) as total from base_product c left outer join prod_incoming a on a.cname=c.cname left outer join prod_outgoing b on b.cname=c.cname
select sum(c.namount) as total from base_product c left outer join prod_incoming a on a.cname=c.cname --and 去掉这个and left outer join prod_outgoing b on b.cname=c.cname
select sum(c.namount) as total from base_product c left outer join prod_incoming a on a.cname=c.cname left outer join prod_outgoing b on b.cname=c.cname
sum(c.namount) as total
from
base_product c
left outer join
prod_incoming a
on
a.cname=c.cname
left outer join
prod_outgoing b
on
b.cname=c.cname
left outer join prod_incoming a on a.cname=c.cname --and 去掉这个and
left outer join prod_outgoing b on b.cname=c.cname
left outer join prod_incoming a on a.cname=c.cname
left outer join prod_outgoing b on b.cname=c.cname