Aggregate modifiers (ORDER BY)

Controlling Order By default, aggregated values have no guaranteed order. Modifiers give you precise control over sequencing. ORDER BY in Aggregates Time-Ordered Arrays The array preserves the sequence with most recent activity first. Downstream code can iterate through these events in order. Removing Duplicates DISTINCT in Aggregates ORDER BY + DISTINCT You can use both modifiers together: This gives you unique categories in alphabetical order for each customer.

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This section is part of the Aggregating: 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 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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