Practical insights
- 1000published
- 25in review
- 8topic families
Results
- Model a many-to-many relationship with a bridge table and state how weights prevent double counting
A booking can carry several promotion codes, and an analyst joins bookings to a promo column to report revenue by promotion.
harddocumented fact - Move fast-changing attributes into a mini-dimension instead of versioning the whole dimension
A customer dimension with millions of rows has a loyalty tier, risk band and credit-limit band that change monthly, and every change makes a type 2 copy of the whole row.
harddocumented fact - Store the zone name for a future local event, not the offset you know today
A schedule table stores departure times for next year as timestamps with a fixed offset computed at load time, and a government changes its daylight-saving rule.
harddocumented fact - Disambiguate repeated local times with an offset or fold before parsing wall-clock timestamps
A gate-system export has local timestamps without offsets, and on the night clocks go back the hour 01:00-02:00 appears twice.
harddocumented fact - Keep two clocks for corrected facts, when it was true and when you learned it
Finance restates last month's revenue after a refund batch is posted, and the dashboard owner overwrites the monthly figures; a model trained on last month's numbers can no longer be reproduced.
hardpractitioner heuristic - Set the late-data allowance from the measured arrival-delay distribution
A streaming job aggregates bookings by event time with an arbitrary 10-minute allowance, and the daily total disagrees with the nightly batch by a stable fraction of a percent.
hardpractitioner heuristic - Match near-duplicate entities with scored comparisons and a clerical-review band
Two passenger files should be merged, names and birth dates are keyed by hand, and exact-match deduplication leaves obvious duplicates while a loose rule merges different people.
harddocumented fact