How to calculate the sum of values in a tree using SQL

Question

I need to sum points on each level earned by a tree of users. Level 1 is the sum of users\' points of the users 1 level below the user. Level 2 is the Level 1 points of the

Answer 1

If you are working with trees stored in a relational database, I'd suggest looking at "nested set" or "modified preorder tree traversal". The SQL will be as simple as that:

SELECT id, 
       SUM(value) AS value 
FROM table 
WHERE left>left\_value\_of\_your\_node 
  AND right<$right\_value\_of\_your\_node;

... and do this for every node you are interested in.

Maybe this will help you: http://www.dbazine.com/oracle/or-articles/tropashko4 or use google.