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分析函数
AVG ( expr )
返回表达式的平均值
Example:
HR@orcl10g> select manager_id, last_name, hire_date, salary,
2 avg(salary) over (partition by manager_id order by hire_date
rows between 1 preceding and 1 following) c_mavg
3 from employees;
HR@orcl10g> select AVG(salary) "Avg Salary" from employees;
Partition by :表示如何分组
Order by :表示排序
Rows between :表示窗口大小
本例中表示本记录上下各取一行进行计算
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