Query for updating a node in hierarchial tree structure
Query for updating a node in hierarchial tree structure - Dateing sex kannda
While XML handles hierarchical data quite well, relational SQL doesn't.There are several different ways to model a hierarchical structure.
In this tutorial , I will explain how to manage hierarchical data using My SQL and PHP.
The next part is to find the root node of the tree, also known as the top-level, or big boss man, etc. That's the node that has no parent (Null), so we will start there and set the Lineage column as the root: WHILE EXISTS (SELECT * FROM Tree WHERE Depth Is Null) UPDATE T SET T.depth = P. The final result is: You'll notice that for each node, the entire lineage back to the root is stored.
This means that finding someone's boss, or their boss' boss, doesn't require any self-joins or recursion to create an indented list.
You may be able to use them more easily than I can, but if you also find them daunting, read on.
So how to represent a hierarchy, using adjacency, and avoiding recursion wherever possible?
Specifically, I will explore the two most popular hierarchical data models: Parent id is actually a category id of the parent category.
This method is quite simple; it is easy to see parent-child relations.The Depth column comes in handy for performing the indent by using the Space() function. will sort the org chart properly, with each subordinate nesting underneath their parent.Sort order is maintained by Node values, and can be changed simply by updating the node value.You can find a person's boss easily, and you can find their coworkers by querying the Boss ID column. It would be great if it could join itself as many times as needed.The trouble begins when you want to list several levels of a hierarchy. Name Employee FROM Employees INNER JOIN Employees AS Boss ON Employees. This is called a recursive join, and though some database products support it (Oracle has the CONNECT BY syntax) SQL Server is not one of them.The most common and familiar is known as the adjacency model, and it usually works like this: It's called the "adjacency" model because the parent (boss) data is stored in the same row as the child (employee) data, in an adjacent column.