For Sun Virtual Box:
use the Right-Ctrl (read: the ctrl key on the right side of your keyboard).
For VM Player:
ctrl + alt
There's more than one reason why you may receive this error, but the most common reason is that your order by statement column list doesn't correlate with your intended column-to-retrieve list when you happen to be using DISTINCT. This is usually easy to spot. A more obscure reason may be that you are using a function around one of the selected columns --but omitting to use the same function around the same selected column name in the order by statement. Here's an example: select distinct upper(columnA) ......