没有CTE的Postgres / PADB中的递归自查询

Question

I am using PADB/Postgres which lacks recursive CTE's. I am trying to find a way to write a recursive self join using only regular joins/unions without recursive CTEs. What is the simplest way to do this?

I have a table like this:

PersonID | Initials | ParentID
1          CJ         NULL
2          EB         1
3          MB         1
4          SW         2
5          YT         NULL
6          IS         5

And I want to be able to get the records only related to a hierarchy starting with a specific person. So If I requested CJ's hierarchy by PersonID=1 I would get:

PersonID | Initials | ParentID
1          CJ         NULL
2          EB         1
3          MB         1
4          SW         2

And for EB's I'd get:

PersonID | Initials | ParentID
2          EB         1
4          SW         2

Answer 1

This is the simplest solution i can think of.

select * from t where personid = '1' --needs replacement with personid you run for
union
select * from t where personid in (select personid from t where parentid = '1')
or parentid in (select personid from t where parentid = '1')

The personid needs replacement with the person you need to see the hierarchy for.

SQL Fiddle: http://sqlfiddle.com/#!15/f1201/1