SQL SERVER has a task table where the id field is the primary key and the parent field is the foreign key pointing to the id, used to describe how multiple nodes form a tree. The root node of a tree is null, and the records with a null parent are the child nodes of the root, that is, the secondary nodes. The weight field only has a value when it is a leaf node.
Now we need to recursively calculate the hierarchical structure of the tree. Parallel nodes are arranged in order of their IDs, and the new name field=level * underline + original name, which is used to visually represent the hierarchical relationship; The new weight field is the sum of the weights of all subordinate nodes, and the level field represents the hierarchy.
SPL code:
A1: Query the database through JDBC.
A2: Create an empty result set.
A3: Filter out the child nodes of the root and loop through these nodes using recursive function.
A4-B6: Function tree, which adds new records to the result set, recursively processes directly subordinate nodes, and returns the weight of the new record. It has four parameters: id, name, weight, and level.
B4: Add new records to the result set and spell out the new name and level. The new weight will be calculated later, so let's set it to 0 for now.
B5: Filter out the direct subordinate nodes of this node, recursively calculate the weights of these nodes, and sum them up.
B6: Calculate the new weight and modify this record to return the new weight.
A7: Return the result set.
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