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SQL Interview Tips 5/100 | Uber Interview #shorts

The video tackles a classic SQL interview challenge: given a table representing a binary tree, produce a result set that labels each node as Root, Inner or Leaf. The presenter walks through the schema, where each row contains a node identifier and its parent identifier, and explains how to derive a new column indicating the node type. The solution hinges on three logical checks. First, a node whose parent field is NULL is classified as the Root. Second, leaf nodes are identified by excluding any node that appears in the distinct list of parent values—if a node never serves as a parent, it must be a leaf. Finally, any remaining nodes that are neither root nor leaf are labeled Inner. These conditions are implemented succinctly with a CASE WHEN expression in a SELECT statement. Key excerpts include, “any such type of node where the parent is null that will be known as our root,” and “leaf nodes are not the parent of any other node, so they are not present in the parent column.” The presenter also demonstrates the use of a NOT IN subquery against the distinct parent set to flag leaves. Mastering this pattern equips candidates to answer a frequent data‑engineering interview question, showcases proficiency with conditional logic in SQL, and prepares them for more complex hierarchical queries. The speaker directs viewers to the Grow Data Skills platform for additional practice problems and structured interview preparation.