We can create planned orders & convert them into purchase requisition or into production order.
In the material master ,MRP2 view give the procurement type as 'X', for both internal & external procurement.
Also include purchasing view for this material.
When you run MRP using md02, a planned order will be created for the requirement (Eg: say 100 no's given using transaction code MD61).
Use transaction code MD04 to view the stock/requirement list.
Here double click the planned order, you can see tabs such as convert into purchase requisition, into production order, into process order.
Click convert into Purchase Requisition & enter 50 Nos. Then a Purchase Requisition will be created which can be further converted into Purchase Order.
Again come to md04 screen.
You can see a planned order & Purchase Requisition for 50 no's.
This planned order can be converted into production order & 50 no's can be produced internally.