我有一个数据库,基本上存储了由几个家庭组成的家谱。
我有两张桌子:
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?
我在很多东西的一个选择中尝试了一个选择,但它不起作用:
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。
答案 0 :(得分:1)
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;