在SQL中的聚合函数帮助？

Question

如果我有以下数据：

Policy Number:       Amount:
100                    200
100                    100
101                    50 
102                    90

我可以在SQL代码中编写什么来获得以下结果而不更改数据

Policy Number:    Amount:
100                 300
101                 50
102                 90

Answer 1

您只需要按非聚合列进行分组：

select 
  [Policy Number], 
  sum(Amount)
from the_table
  group by [Policy Number]

Answer 2

SELECT PolicyNumber, SUM(Amount) FROM Table GROUP BY PolicyNumber

Answer 3

Select policy_number, sum(amount) as amount
from table_name
group by policy_number
order by 1