Turning millions of records into a single, accurate number is one of the most valuable skills a backend developer can have.
1Clean Result Sets
When building APIs, your frontend developers will thank you for using clear aliases. Instead of parsing row['COUNT(id)'], they can simply use row.total_users.
2Conditional Counting
A pro tip: you can combine aggregates with CASE statements for powerful reporting, but for now, focus on mastering the combination of WHERE and COUNT to find specific subsets of data.
3Nulls in Math
Be careful: SUM() and AVG() ignore NULL values. If a product has no price (NULL), it won't be counted in the average. This is usually what you want, but you must be aware of it!
