如何解决SQL:显示孩子和兄弟/姐妹
我有两张桌子:
- "persons": id,name,lname
- “关系”:父母、孩子
显示所有父母没问题,我是这样做的:
SELECT disTINCT p.fname,p.lname
FROM persons p
INNER JOIN relationships ON p.id = relationships.p
INNER JOIN persons c ON c.id = relationships.c;
但是我怎样才能全面地展示每个孩子及其各自的兄弟/姐妹?
SELECT disTINCT
c1.name,c1.lname,(
SELECT
c2.firstname,c2.lastname
FROM
persons p2
INNER JOIN relations ON p2.id = relations.parent
INNER JOIN persons c2 ON c2.id = relations.child
WHERE
p.id = p2.id
)
FROM
persons p
INNER JOIN relations ON p.id = relations.parent
INNER JOIN persons c1 ON c1.id = relations.child;
我认为我走错了路。
感谢您的帮助。
解决方法
如果我理解正确,这只是一个自连接:
select r.child,r2.child as sibling
from relationships r join
relationships r2
on r.parent = r2.parent and
r.child <> r2.child
order by r.child,r2.child;
对于来自另一个表的名称,您需要更多连接:
select p.*,p2.*
from relationships r join
relationships r2
on r.parent = r2.parent and
r.child <> r2.child join
persons p
on p.id = r.child join
persons p2
on p2.id = r2.child
order by r.child,r2.child;
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