Deterministic Ordering
Without a unique sort order, SQL may return tied rows in any order — so top-N lists, pages, and “latest record” picks can change between runs.
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When Correct SQL Returns the Wrong Answer
A query can run cleanly and still answer a different question. See how joins, NULLs, ordering, and aggregation levels change results, and how to catch it.
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SQL for Data Engineers
Understand SQL through examples for filtering, cleaning, joins, aggregation, windows, and transactions in DuckDB.