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  3. you've studied graph theory in computer science classes you'll remember that the order of child nodes in a tree is irrelevant to the graph. That is, (R (F) (M) (L)) is the same tree as (R (M) (L) (F)).So keep in mind that display order data properly should be separate from the hierarchy data.But since path enumeration is essentially a denormalized solution already, perhaps we can bend the rules.Therefore you could just make sure to update the primary key values of tree nodes, so that the natural order of these values matches your desired display order.This is admittedly a fragile solution, and pretty much a hack of coupling the sibling order to the primary key values (which should be arbitrary and independent of meaning).This illustrates that each solution to represent trees in SQL has its strengths and weaknesses, and therefore which design you use should be based on the types of queries you need in a given application.It would take a whole book to compare how to implement every scenario in all the designs of trees. In my book "SQL Antipatterns," I had to limit myself to 20 pages on hierarchical data, because there are other topics to cover. car insurance rate

  4. Consider a transformation of a tree like (A (B (D (F (H, I))), C (E (G)))) -> (A (B (D), C (E (G (F (H, I))))))That is, move a subtree F with its children H and I. Old parent is D. New parent is G.Paths within the subtree (e.g. FF, HH, II, FH, and FI) don't need to change at all. Keep in mind the "depth" is really pathlength, not the level in the tree.Paths from ancestor nodes into the subtree have to be recalculated, up to the common ancestor of the old parent and the new parent.I can update paths from D and simply change the parent to G, and pathlengths stay the same. I can delete paths from B into the moving subtree. And I can insert new paths from C and E into the subtree, generating the paths I need by joining CE and CG to the paths inside the subtree, and adding 1 to the pathlengths. Paths from A into the subtree need to add 1 to pathlength because the length from A to G is 1 greater than the length from A to D.Hmm. I'm thinking I could write a whole book showing how to do each type of tree operation with each type of hierarchical data design. Maybe that'll be my next book. car insurance quotes auto insurance quotes online in Chicago IL car insurance quotes in NY

  5. Hi,I found your slides on Slideshare after posting a question on phpfreaks and believe it I've been using it a lot. Not just for the closure table approach but for enums and other goodies that were in there so thank you for this document.I have question regarding the closure table. I have a tree structure that is working well. Now I want to copy a node and all its children and I am having a hard time finding the right approach to do it. When I copy for instance node A with children B and C, it will create Notes A' B' C' with new IDs ( I have an auto-incrementprimary key) Reproducing the relationship OF A, B and C poses me a challenge however. In the closure table you have the relations regarding the original nodes but you cannot build reproduce the relation with the new nodes as they were just created and there's no information about them in the closure table. Do you have any suggestion as to how I should tackle this? Thanks in advance, JR from Montreal credit card rates good cash reward credit card

  6. I've never said “none” want to blog. The vast majority don't want to blog. As long as it less than a majority, then the phrase, by the standards of modern journalism, is correct. The fact that 1 or 2% of employees want to blog is not even statistically significant. It's certainly worth noting, and likely will increase, but by and large employees do not want to blog. Close to 60% of organizations have blogs on their intranet now, and this is a sign of things to come. Work cultures will evolve in the years to come and more employees will no doubt embrace blogging, but not right now.Again, I never said employees “shouldn't” blog. My contention is that close to 99% don't want to, but most want to read them from executives. My assertion is therefore that Executives should blog, not employees. This doesn't mean all executives, nor all employees. Its a general statement that is correct by the standards of the English language. credit cards with frequent flier miles

  7. I love the degrees of siearpteon on LinkedIn. It’s concise and accurate. It’s one of my favorite functions of that platform. I’m a senior in college for Arts Management with a secondary focus on Social Media and would love to hear what others have to say about this.

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