<ul><li>A certain table in the MS SQL database has a multi-level self-association structure, where the second field parent node ID is a foreign key pointing to the first field node ID of the table, and the third field is a zone.</li><li>The task is to find the hierarchy of nodes with a higher level of 2 or more, as well as the zones of the highest-level nodes.</li><li>The SQL solution uses complex recursive subqueries and self joins, making the code lengthy and difficult to understand.</li><li>The SPL solution provides directly available functions to obtain all levels of recursive references to nodes, making the code simpler and more manageable.</li></ul>

Calculate the Hierarchy of Recursive References — From SQL to SPL #11

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