Implement in-memory DB querying

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Implement an in-memory database that supports: 1. Querying the whole table and returning only selected columns (projection). 2. Adding WHERE clause filtering with simple conditions like (column, operator, value). 3. Adding ORDER BY on one or more columns with ascending/descending control. 4. Explaining how you would design and build an index to accelerate such queries (no code required).  Example public API: db = DB() db.insert("users", {"id": "1", "name": "Ada", "birthday": "1815-12-10"}) … db.query("users", ["id"], conditions=[("name", "=", "Charles")], order_by=(["birthday"], False))  # returns sorted projection

PracHub · Accepted Answer

This question evaluates a candidate's competency in data structures, algorithms, and systems-level thinking for implementing query processing in an in-memory database, including projection, predicate filtering, ordering, and index design.

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Implement in-memory DB querying