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+2  Q: 

Best way to retrieve hierarchical data from database

I have to store blog style comments in a database. Each comment can have a parent one.

I am doing it with a column called "parentComment" that has a null value when it is a top level comment or have a value if it is a response to another comment.

What is the most efficient way to retrieve a comment and all its childs?

+1  A: 

A quite common technique is to also have a (duplicate, indirectly) relation to the "root" of the tree, which means you can select the full tree in one neat select. Othewise it quickly gets dirty.

krosenvold  2008-12-11 17:30:17

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