Use COUNT(DISTINCT) across joins and understand distinct counting in aggregation
I want to see regional rep coverage — for each region (include all of them), how many distinct sales reps have closed at least one deal there? Also show the total number of transactions and total revenue. I want all regions listed even if the count is zero.
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LEFT JOIN dim_regions to fact_sales to keep EMEA (the ghost region) in results
COUNT(DISTINCT s.employee_id) gives you unique reps per region
Use COALESCE for the zero-sale region to avoid NULLs