DATE_DIFF()

Concepts covered: sqlDateDiff

Calculating Time Differences Calculating Days Between The most common use case is calculating the number of days between two events: Different Time Units Practical Applications Age Calculations One of the most common uses is calculating ages from birth dates. The year difference gives approximate age. For exact age that accounts for whether the birthday has passed this year, additional logic is needed, but year difference covers most use cases. SLA Metrics This query calculates how many hours each ticket took to resolve. With a 24-hour SLA, tickets T001 (5 hours) and T003 (18 hours) met the target, while T002 (54 hours) exceeded it. Best Practices When to Use DATE_DIFF() These are the most common scenarios where calculating time differences is essential. With these use cases in mind, here

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This section is part of the Dates: 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 PostgreSQL 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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