SQL：显示children和brothers/sisters

Question

我有一个数据库，主要存储由多个家庭组成的家谱。

我有两个表：

"persons": id, name, lname
“关系”：parent、child

显示所有 parent 没问题，我这样做了：

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显示每个 child 及其各自的 brothers/sisters？

我在 select 中尝试了 select，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;

我想我走错了路。

感谢您的帮助。

Answer 1

如果我没理解错的话，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;

对于来自其他 table 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;

SQL：显示children和brothers/sisters

SQL: display children and brothers/sisters

sql

foreign-keys

inner-join