Half-Open Intervals vs BETWEEN

Concepts covered: sqlRecursiveCte

The two areas where date arithmetic ships the most bugs in production: timezone handling and engine portability. Both have specific patterns and known mitigations. Naming them in the interview, even briefly, reads as production-experience that the basic-syntax candidate does not have. The timezone gotcha Daylight saving time creates a specific failure mode. In US Eastern, the local clock skips 2 AM in March and repeats 1 AM in November. A timestamp '2024-03-10 02:30 US/Eastern' does not exist; engines either throw or default to the next valid time. A timestamp '2024-11-03 01:30 US/Eastern' is ambiguous; it occurs twice. UTC has no DST; comparisons and arithmetic in UTC are unambiguous. The production rule: store timestamps as UTC; do timezone conversion at the display layer only. Engine po

About This Interactive Section

This section is part of the Date Arithmetic: Beginner 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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DataDriven combines four interview rounds (SQL, Python, Data Modeling, Pipeline Architecture) with adaptive difficulty and spaced repetition. Easy problems get harder as you improve. Weak concepts resurface until you master them. Your readiness score tracks progress across every topic interviewers test. Every lesson section ends with problems you solve by writing and running real code, not by picking multiple-choice answers.