What are window functions in MySQL 8.0, and how do they differ from aggregate functions?
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.
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Compute a single result over a set of rows (e.g., SUM, AVG, COUNT, MAX, MIN).
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Collapse multiple rows into a single output row when used with GROUP BY.
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Cannot access individual row values once aggregated.
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Perform calculations across a set of rows called a window, which can be defined using PARTITION BY and ORDER BY.
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Do not collapse rows; each row retains its identity.
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Can access values from other rows in the same window (e.g., running totals, rankings, moving averages).
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Aggregate functions collapse rows; window functions do not.
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Window functions can perform calculations relative to the current row.
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Aggregate functions require GROUP BY to operate over sets of rows; window functions use OVER() with optional PARTITION BY and ORDER BY clauses.
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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.