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What is a MERGE (upsert), and how do you use it for incremental loads and SCDs?

MERGE handles insert-or-update-or-delete in one statement, the backbone of incremental loads and slowly-changing dimensions. The signal is the matched/not-matched logic and what makes a retry safe.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.

MERGE handles insert-or-update-or-delete in one statement, the backbone of incremental loads and slowly-changing dimensions. The signal is the matched/not-matched logic and what makes a retry safe.

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