Fix #94 - Added "Better" example in G-3310

Author: kibeha

docs/4-language-usage/3-dml-and-sql/3-transaction-control/g-3310.md

@@ -63,4 +63,24 @@ begin
    commit;
 end;
 /
+```
+
+## Example (better)
+
+(Assuming suitable foreign key relationship exists to allow updating a join.)
+
+``` sql
+begin
+   update (
+      select o.customer_id, ol.discount
+        from orders o
+        join order_lines ol
+             on ol.order_id = o.order_id
+       where o.order_status = 'New'
+   )
+   set discount = sales_api.calculate_discount(p_customer_id => customer_id);
+
+   commit;
+end;
+/
 ```