Window Function Concepts and Syntax +------+---------+------------+--------+ | 2000 | Finland | Computer | 1500 | | 2000 | Finland | Phone | 100 | | 2001 | Finland | Phone | 10 | | 2000 | India | Calculator | 75 | | 2000 | India | Calculator | 75 | | 2000 | India | Computer | 1200 | | 2000 | USA | Calculator | 75 | | 2000 | USA | Computer | 1500 | | 2001 | USA | Calculator | 50 | | 2001 | USA | Computer | 1500 | | 2001 | USA | Computer | 1200 | | 2001 | USA | TV | 150 | | 2001 | USA | TV | 100 | +------+---------+------------+--------+ mysql>  SELECT SUM(profit) AS total_profit FROM sales; +--------------+ | total_profit | +--------------+ | 7535 | +--------------+ mysql>  SELECT country, SUM(profit) AS country_profit FROM sales GROUP BY country ORDER BY country; +---------+----------------+ | country | country_profit | +---------+----------------+ | Finland | 1610 | | India | 1350 | | USA | 4575 | +---------+----------------+ mysql>  SELECT year, country, product, profit, SUM(profit) OVER() AS total_profit, SUM(profit) OVER(PARTITION BY country) AS country_profit FROM sales ORDER BY country, year, product, profit; +------+---------+------------+--------+--------------+----------------+ | year | country | product | profit | total_profit | country_profit | +------+---------+------------+--------+--------------+----------------+ | 2000 | Finland | Computer | 1500 | 7535 | 1610 | | 2000 | Finland | Phone | 100 | 7535 | 1610 | | 2001 | Finland | Phone | 10 | 7535 | 1610 | A window function performs an aggregate-like operation on a set of query rows. However, whereas an aggregate operation groups query rows into a single result row, a window function produces a result for each query row: For example, using the sales information table, these two queries perform aggregate operations that produce a single global sum for all rows taken as a group, and sums grouped per country: •The row for which function evaluation occurs is called the current row. •The query rows related to the current row over which function evaluation occurs comprise the window for the current row. By contrast, window operations do not collapse groups of query rows to a single output row. Instead, they produce a result for each row. Like the preceding queries, the following query uses  SUM() , but this time as a window function: 2425