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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Data Model Change and Compatibility
The dangerous model change is the one that passes every check. See what breaks consumers, why meaning changes are invisible, and how to publish one safely.
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Modeling Time, History, and Corrections
“What was true then” and “what did we believe then” are different questions. See which clocks a model needs, and how corrections keep both answerable.
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Fact Table Grain and Aggregation
Wrong totals rarely raise an error. See why grain is a contract, which facts you may not sum, and the join that inflates a number without warning.
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Operational vs Analytical Data Models
Operational and analytical models face different pressures for writes, scans, meaning, and history. See what each protects and how to connect them.