Window Functions vs Aggregate Functions in MySQL 8.0
MySQL 8.0 introduced window functions, which allow performing calculations across a set of rows related to the current row without collapsing the result set. They are different from traditional aggregate functions in their behavior and use.
Compute a single result over a set of rows (e.g., SUM, AVG, COUNT, MAX, MIN).
Collapse multiple rows into a single output row when used with GROUP BY.
Cannot access individual row values once aggregated.
Perform calculations across a set of rows called a window, which can be defined using PARTITION BY and ORDER BY.
Do not collapse rows; each row retains its identity.
Can access values from other rows in the same window (e.g., running totals, rankings, moving averages).
Aggregate functions collapse rows; window functions do not.
Window functions can perform calculations relative to the current row.
Aggregate functions require GROUP BY to operate over sets of rows; window functions use OVER() with optional PARTITION BY and ORDER BY clauses.
Window functions enable advanced analytics like ranking, running totals, and moving averages within partitions.
In summary: Use aggregate functions when you need summary results that reduce multiple rows into one. Use window functions when you need row-level analysis while still considering a set of related rows.