Row-level vs aggregate behavior

Understanding Differences Row-level and aggregate operations follow different execution models. Grasping this distinction is key to writing correct SQL. Two Worlds of SQL SQL has two fundamentally different kinds of operations: How They Work Together Here's the key insight: row-level operations happen first, for each row individually. Then aggregate functions collect those results and summarize them. Consider this query: Here's the execution order: CASE in Aggregates Patterns and Pitfalls Understanding what works and what doesn't helps you avoid common mistakes when mixing row-level and aggregate operations. Reverse Doesn't Work Why doesn't this work? Think about when things happen: It's like trying to know the final score of a game before it's played. The aggregate hasn't happened yet whe