Generating Date Spines and Filling Gaps

Concepts covered: sqlDateVsTimestamp

The four platform-level date concerns Four concerns recur across every platform-team conversation about dates. First: bitemporal modeling. Every row in a reporting table has two times: when the event happened in the business (business time) and when the system observed it (system time). Reports that confuse the two produce restated numbers without anyone noticing. Second: watermarking. Date-aware incremental pipelines decide how to handle data that arrives after the watermark; the choice between dropping, reprocessing, or holding is a design call with operational consequences. Third: calendar versioning. Fiscal calendars change. The query that ran correctly last year may produce wrong numbers this year because the company restructured. SCD-2 on the calendar table is the discipline. Fourth:

About This Interactive Section

This section is part of the Date Arithmetic: Advanced lesson on DataDriven, a free data engineering interview prep platform. Each section includes explanations, worked examples, and hands-on code challenges that execute in real time. SQL queries run against a live database. Python runs in a sandboxed Docker container. Data modeling problems validate against interactive schema canvases. All content is framed around what data engineering interviewers actually test at companies like Meta, Google, Amazon, Netflix, Stripe, and Databricks.

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