Grouping a column in oracle

I have three columns within my table: Amount, OrderNumber, Customerid

For each customerid there will be ordernumber and amount. Now i need to display customerid,Ordernumber and Amount(total Amount- for each customerid).

custid  srcnumber   amount
112     4344        20
112     7678        10
112     8766        30
34      6577        15
34      4566        5

Expected:

custid  srcnumber   amount
112     4344        60
112     7678        60
112     8766        60
34      6577        20
34      4566        20

Answer

Use sum() over (partition by ..) analytic function to sum up the amount per each row :

 select Customerid as custid,
        OrderNumber as srcnumber,
        sum(amount) over ( partition by Customerid ) as amount
   from tab
  order by custid desc

Demo