nested-set-model

I want a simple predicate that returns me all the groups which have mode = 0 and the mode of the enrollments in the group = 0 To be precise i need a predicate to access the nested object properties. Somehow a predicate like: [NSPredicate predicateWithFormat:@"mode = 0 AND enrollments.Enrollment.mode = 0"] the above predicate is wrong and obviously doesn't work. EDITED: I have given a go to the following predicate too but been unsuccessful. [NSPredicate predicateWithFormat:@"mode = 0 AND ALL ( SUBQUERY(enrollments,$varEnrollment,$varEnrollment.mode = 0))"] I need result which contains all

There are two ways to work with hierarchy data in MySQL : Adjacency List Model Nested Set Model A major problem of the Adjacency List Model is that we need to run one query for each node to get the path of the hierarchy. In the Nested Set Model this problem does not exist, but for each added node is necessary to give a MySQL UPDATE on all others left and right value. My hierarchical data is not static data, such as product categories of e-commerce. Are constant registration of users in hierarchical sequence. In my application, while there are many constants users registration, I also need to

I've been using the crap out of the Nested Set Model lately. I have enjoyed designing queries for just about every useful operation and view. One thing I'm stuck on is how to select the immediate children (and only the children, not further descendants!) of a node. To be honest, I do know of a way - but it involves unmanageable amounts of SQL. I'm sure there is a more straightforward solution. Did you read the article you posted? It's under the heading "Find the Immediate Subordinates of a Node" SELECT node.name, (COUNT(parent.name) - (sub_tree.depth + 1)) AS depth FROM nested_category AS node

Let's dig in the main problem right away, I have the input like this $category = array( 'A' => array('left' => 1, 'right' => 8), 'B' => array('left' => 2, 'right' => 3), 'C' => array('left' => 4, 'right' => 7), 'D' => array('left' => 5, 'right' => 6), 'E' => array('left' => 9, 'right' => 10), ); I want the output to be something like this $tree = array( array('A', 'B'), array('A', 'C', 'D'), array('E'), ); which one is the best and fast function to loop though the input array and create the output result like this ? Working with a nested set is a perfect case for recursion. Given your data: