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Iterative Query

Author

Topic

madhivanan
Premature Yak Congratulator

22864 Posts

Posted - 2004-12-08 : 08:37:15

I have a table called relations having these records

Id Description Pid
1 x 0
2 z 0
3 a 2
4 b 2
5 c 1
6 n 1
7 p 4
8 r 3
9 s 2
10 t 6

I want to write a query to get all the relations
eg t's Pid is 6 which is id for n who has pid 1 which id for x
So the relation for t is t-n-x
similarly p has p-b-z

I used the following query

select * from(
Select R1.Description as "D5", "" as "D6" ,
"" as "D7" from Relations R1 where R1.Pid=0
union Select R1.Description as "D5", R2.Description as "D6" ,
"" as "D7" from Relations R1, Relations R2 where R1.Pid=R2.id and R2.Pid=0
union Select r1.D3,t1.d1 , t1.D2 from(
Select R1.Description as "D1", R2.Description as "D2" from Relations R1, Relations R2 where R1.Pid=R2.id) as t1,
(Select R1.Description as "D3", R2.Description as "D4" from Relations R1, Relations R2 where R1.Pid=R2.id ) r1
where r1.d4=t1.d1 ) t order by len(d7) asc, len(d6) asc,d5

which produced

D5 D6 D7
x
z
a z
b z
c x
n x
s z
p b z
r a z
t n x

But its working for maximum of three relations
How can I modify this query so that it will return the relations for any level

Thanks in advance

Madhivanan

Seventhnight
Master Smack Fu Yak Hacker

2878 Posts

Posted - 2004-12-08 : 09:03:58

I'd say try reading through http://www.seventhnight.com/treestructs.asp,
but it seems to be down right now...

There is also: http://www.nigelrivett.net/RetrieveTreeHierarchy.html

and also: http://www.sqlteam.com/item.asp?ItemID=8866

EDIT: http://www.seventhnight.com/treestructs.asp should be back up in a few hours (sorry