窗口函数

postgre中的窗口函数相关的内容。从官方的手册中，有很好的说明。

资源

http://postgres.cn/docs/13/tutorial-window.html

http://postgres.cn/docs/13/functions-window.html

http://postgres.cn/docs/13/sql-expressions.html#SYNTAX-WINDOW-FUNCTIONS

SELECT sum(salary) OVER w, avg(salary) OVER w
  FROM empsalary
  WINDOW w AS (PARTITION BY depname ORDER BY salary DESC);