Question

I’m certain this is very easy, but I am very poor at database stuff…

I have the following table in access 2003:

title        |     id
/root        |      1
/root/x      |      2
/root/x/y    |      3
/root/x/y/z  |      4
/root/x/a    |      5
/root/x/a/b  |      6

i.e. a bunch of nodes and id numbers – you can see that /root/x is the parent of /root/x/y. I’d like to create another table which has a list of all the nodes, along with the id’s of their parents. i.e:

id  | parent id
1   |   -
2   |   1
3   |   2
4   |   3
5   |   2
6   |   5

The follwing will give me the id and the value of the parent:

select id, left(c.title, instrrev(c.title, "/")-1)  as parentValue from nodeIDs

yields

id |  parentNode
1  |
2  |  /root 
3  |  /root/x 
4  |  /root/x/y
5  |  /root/x
6  |  /root/x/a

What is the extra step needed to return the id’s of those parent nodes, rather than their values, i.e, return ‘1’ instead of ‘/root’ in that last table?

Many thanks

Answer 1

Something like this perhaps:

select c.id, 
left(c.title, instrrev(c.title, "/")-1)  as parentValue
, p.id as parentID
from nodeIDs c
left join
nodeIDs p
on left(c.title, instrrev(c.title, "/")-1) = p.title