Questions about Nested Intervals by Vadim Tropashko one more time
Date: 1 Dec 2003 20:47:04 GMT
Message-ID: <bqg9c8$qu4$1_at_news.netmar.com>
Hello everybody,
I would like to touch Nested Intervals by Vadim Tropashko one more time. It seems to me that it is the best implementation of storing Trees in SQL, and I want to implement few functions based on Vadim's algorithm:
- Insert new node under ANY other node, such as insert new node "p" under x.z.y.k.d to get the whole path to new node as x.z.y.k.d.p
- Move ANY node in the tree under another node, such as for the two branches x.z.y.k.d.p.k.t and x.w.f.g.i, move branch y.k.d.p.k.t under node f, to get x.w.f.y.k.d.p.k.t
For the 1), I tried to use sample code from "More pain and suffering with Tropashko's materialized path..." thread, http://dbforums.com/arch/57/2003/9/917999, and sample and formulas, http://www.scenic-route.com/program/db/lists3.htm to calculate Numerator
CREATE FUNCTION dbo.Calculate_Numerator
( _at_numer INTEGER, @child INTEGER )
RETURNS INTEGER
AS
BEGIN
RETURN _at_numer * POWER ( 2, @child ) + 3 - POWER ( 2, @child )
END
It seems to me that Denominator depends only of _at_child, so
Calculate_Denominator looks this:
CREATE FUNCTION dbo.Calculate_Denominator
( _at_child INTEGER )
RETURNS INTEGER
AS
BEGIN
RETURN POWER ( 2, _at_child )
END
Now, I am trying to test it against the sample
http://www.scenic-route.com/program/db/lists3.htm, Tropashko Nested
Intervals:
Category Path Numer Denom a__ .1 3 2 | b__ .1.1 7 4
| e .1.1.1 15 8
| f__ .1.1.2 27 16
| k .1.1.2.1 55 32
| g .1.1.3 51 32
| c__ .1.2 11 8
| h .1.2.1 23 16
| i .1.2.2 43 32
| d .1.3 19 16
For the node a_, path .1, SELECT dbo.Calculate_Numerator ( 1, 1 ), I get 3 node a -> b, path .1.1, SELECT dbo.Calculate_Numerator ( 2, 2 ), I get 7 node a -> b -> e, path .1.1.1, SELECT dbo.Calculate_Numerator ( 3, 3 ), I get 19, but it should be 15
Could you explain what is wrong with parameters of calls, and how they should be different for .1.1.2.1, and .1.1.3 calls, for example? What should be _at_child and @numer for this x.z.y.k for example?
For 2) do you have any ideas about implementation?
Thanks,
Alex
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