Window aggregate functions can take literals, literal expressions, column names (sales, for example), or column expressions (sales + profit) as arguments.
Window aggregates can also take regular aggregates as input parameters to the PARTITION BY and ORDER BY clauses. The RESET WHEN clause can take an aggregate as part of the RESET WHEN condition clause.
COUNT can take "*" as an input argument, as in the following SQL query:
SELECT city, kind, sales, profit, COUNT(*) OVER (PARTITION BY city, kind ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) FROM activity_month;