Have you ever watched a generated SQL refactor run faster and assumed it must be correct? That assumption breaks down when the speedup comes from an inner join that silently drops rows the old left join preserved. The output still looks plausible because every displayed row has a customer name,...
Source: [Dev.to](https://dev.to/codepy_1473/a-generated-sql-query-got-faster-by-returning-fewer-rows-test-that-before-you-merge-it-h50)