select a.* , b.* , c.* from a left join b on a.条件 = b.条件 left join c on b.条件 = c.条件select a.* , b.* , c.* from a left join b on a.条件 = b.条件 left join c on a.条件 = c.条件这得看你的条件怎么定了?
select a.* , b.* , c.* from a left join b on a.条件 = b.条件 left join c on b.条件 = c.条件红色部分意思不是a left join c吗?那后面条件能成立吗?
个人喜欢用+操作代替join操作符, join操作符可读性太差,写起来麻烦
select a.*,b.*, c.* from a, b, c where a.条件 = b.条件(+) and b.条件 = c.条件(+) and....
( ... A left join B on ...) AB left join C on ... 无限外联下去·····
left join b on a.条件 = b.条件
left join c on b.条件 = c.条件select a.* , b.* , c.* from a
left join b on a.条件 = b.条件
left join c on a.条件 = c.条件这得看你的条件怎么定了?
left join b on a.条件 = b.条件
left join c on b.条件 = c.条件红色部分意思不是a left join c吗?那后面条件能成立吗?
join操作符可读性太差,写起来麻烦
where a.条件 = b.条件(+)
and b.条件 = c.条件(+)
and....
无限外联下去·····