Question: Hallo,
I have a join table, said tableA and tableB. tableA have a column called Amount. tableB have a column called refID. I would like to total up the Amount column when refID having the same value. I was using SUM in my query, but it throw me an error:

```
ORA-30483: window  functions are not allowed here
30483. 00000 -  "window  functions are not allowed here"
*Cause:    Window functions are allowed only in the SELECT list of a query.
           And, window function cannot be an argument to another window or group
           function.

```

Here is my query for your reference:

```
select *
from (
       select SUM(A.Amount), B.refId, Rank() over (partition by B.refID order by B.id desc) as ranking
       from table A
       left outer join table B on A.refID = B.refID
)
where ranking=1;

```

May I know is there any alternate solution in order for me to SUM the Amount?

THanks @!

Answer: 
```
SELECT  *
FROM    (
        SELECT  A.Amount, B.refId,
                Rank() over (partition by A.refID order by B.id desc) as ranking,
                SUM(amount) OVER (PARTITION BY a.refId) AS asum
        FROM    tableA A
        LEFT JOIN
                tableB B
        ON      B.refID = A.refID
        )
WHERE   ranking = 1

```
```
SELECT refid, sum(a.amount)
FROM table AS a LEFT table AS b USING (refid)
GROUP BY refid;

```