I have this table

| ID | TYPE | AMOUNT |
| --- | --- | --- |
| 1 | - | 1234 |
| 2 | + | 4567 |

I want column amount to be displayed like this

| ID | TYPE | AMOUNT |
| --- | --- | --- |
| 1 | - | -1234 |
| 2 | + | 4567 |

I tried

```
SELECT
    a.* , 
    CASE 
        WHEN a.type = '-' 
            THEN a.AMOUNT * -1 
            ELSE 'null' 
    END
FROM
    dual a

```

but it's not working because data format.

Can someone help me?

Thanks!