Deleting hierarchical data in SQL table

Question

I have a table with hierarchical data.
A column \"ParentId\" that holds the Id (\"ID\" - key column) of it\'s parent.

When deleting a row, I want to delete all c

Answer 1

Depends how you store your hierarchy. If you only have ParentID, then it may not be the most effective approach you took. For ease of subtree manipulation you should have an additional column Parents that wouls store all parent IDs like:

/1/20/25/40

This way you'll be able to get all sub-nodes simply by:

where Parents like @NodeParents + '%'

Second approach
Instead of just ParentID you could also have left and right values. Inserts doing it this way are slower, but select operations are extremely fast. Especially when dealing with sub-tree nodes... http://en.wikipedia.org/wiki/Tree_traversal

Third approach
check recursive CTEs if you use SQL 2005+

Fourth approach
If you use SQL 2008, check HierarchyID type. It gives enough possibilities for your case. http://msdn.microsoft.com/en-us/magazine/cc794278.aspx