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

SQL in general, like others said, does not handle well such relations. Typically, a surrogate 'relations' table is needed (id, parent_id, unique key on (id, parent_id)), where:

• every time you add a record in 'table', you:

  INSERT INTO relations (id, parent_id) VALUES ([current_id], [current_id]);

  INSERT INTO relations (id, parent_id) VALUES ([current_id], [current_parent_id]);

  INSERT INTO relations (id, parent_id) SELECT [current_id], parent_id FROM relations WHERE id = [current_parent_id];

• have logic to avoid cycles

• make sure that updates, deletions on 'relations' are handled with stored procedures

Given that table, you want:

SELECT rel.parent_id, SUM(tbl.points)
FROM table tbl INNER JOIN relations rel ON tbl.id=rel.id
WHERE rel.parent_id <> 0
GROUP BY rel.parent_id;