Filtering a Date Range Correctly

Concepts covered: sqlDateDiff

EXTRACT pulls a part out of a date or timestamp value. EXTRACT(YEAR FROM txn_date) returns 2024 from the date '2024-03-15.' EXTRACT(MONTH FROM ...) returns 3. EXTRACT(DOW FROM ...) returns the day of week (0-6, with 0 being Sunday on most engines). EXTRACT is the tool for filtering by date component (only December rows; only Mondays) or for grouping by date component (revenue per month-of-year across all years). The EXTRACT pattern Available EXTRACT fields Standard fields: YEAR, QUARTER, MONTH, WEEK, DAY, DAYOFYEAR, DAYOFWEEK (or DOW), HOUR, MINUTE, SECOND, EPOCH (Unix seconds since 1970). Each engine has its own conventions for DAYOFWEEK numbering. Postgres ISO: 0 = Sunday, 6 = Saturday. MySQL: 1 = Sunday, 7 = Saturday. BigQuery: 1 = Sunday, 7 = Saturday. Snowflake: depends on session set

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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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