在SQL中的聚合函數幫助？

Question

如果我有以下數據：

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

我可以在SQL代碼寫什麼得到以下結果不改變數據

Policy Number: Amount: 
100     300 
101     50 
102     90 

Answer 1

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

Answer 2

你只需要組由非聚集列像這樣：

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

Answer 3

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