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If you're primarily going to read the tree, it might be advantageous to store pointers to every ancestor instead of just the direct parent. You can query for all the ancestors in one query, and then build the path in Perl. For example,

Nodes ===== id | node_name | parent ----+------------------+-------- 1 | Parent Node1 | 0 2 | Child Node 1 | 1 3 | Sub Child Node 1 | 2 4 | Leaf1 | 3 HasAncestor =========== child | ancestor -------+---------- 2 | 1 3 | 2 3 | 1 4 | 3 4 | 2 4 | 1 SELECT Nodes.* FROM Nodes LEFT JOIN HasAncestor ON Nodes.id = HasAncestor.child WHERE Nodes.id = ? Returns for args (3) ==================== id | node_name | parent ----+------------------+-------- 1 | Parent Node1 | 0 2 | Child Node 1 | 1 3 | Sub Child Node 1 | 2

This way, you can easily fetch an entire subtree. For example,

SELECT Nodes.* FROM Nodes LEFT JOIN HasAncestor ON Nodes.id = HasAncestor.child WHERE HasAncestor.ancestor = ? Returns for args (2) ==================== id | node_name | parent ----+------------------+-------- 3 | Sub Child Node 1 | 2 4 | Leaf1 | 3

You can still fetch only the immediate children. For example,

SELECT Nodes.* FROM Nodes WHERE Nodes.parent = ? Returns for args (2) ==================== id | node_name | parent ----+------------------+-------- 3 | Sub Child Node 1 | 2

Similar for the immediate parent.


In reply to Re: Tree Structure and Db by ikegami
in thread Tree Structure and Db by InfiniteLoop

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