mysql - ForeignKey 引用同一个表

Question

有一个面试测试，下面是表格和结构

 Table Person = id, name, dob, dod, mother_id, father_id
 Primary Key (id)
 Foreign Key mother_id references Person
 Foreign Key father_id references Person

有人问了

1. "select all who are mothers"
2. "select those child who are children of 'John Smith' and 'Jane'

我很困惑，因为我假设外键会像往常一样与其他表链接。但那时我失败了。有人知道实际的答案和原因吗？

Answer 1

这种数据结构称为“自引用表”

SELECT DISTINCT mothers.*
FROM person
    inner join person mothers on person.mother_id = mothers.id

和

SELECT person.*
FROM person
    inner join person fathers on person.father_id = fathers.id
    inner join person mothers on person.mother_id = mothers.id
WHERE 
    fathers.name='john smith'
and 
    mothers.name='jane'