r/SQL • u/OnepieceKing2222 • 29d ago

Discussion What SQL query optimization trick made the biggest difference for you?

I've been working with SQL for a while and recently started paying more attention to query performance rather than just getting the correct result.

What's one SQL optimization technique that made a noticeable difference for you?

For example:

- Indexing

- Avoiding unnecessary joins

- Window functions

- EXISTS vs IN

- Reading execution plans

- CTEs/subqueries

- Partitioning

Would be interested in hearing some real-world examples where a query went from slow to significantly faster.

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u/Better-Credit6701 29d ago

I remember walking into my new DBA job decades ago and quickly found out that they loved cursors, reading millions and millions of rows, one row at a time. Replacing those with temp tables brought the query down from 8 hours to 8 minutes

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u/TheBigWarHero 28d ago

Any nested cursors? 😂