Calculating new Field

Hi All,

I need to populate a new field via sql Which uses values from two Tables. These Include the Prod. Order Line and Prod. Order Components. I'm trying to get a "Pick Qty Outstanding" which is essentailly..

( Prod Order Line."Quantity" * Prod. Order Component."Quantity Per") - Prod. Order Component."Qty. Picked"

The new field will be on the Prod. Order Component Table.

Can anyone advise me on how to do such joins in SQL. Thanks