connection between inventory and purchase cycle

Hi SAP users,

plz help me out with the following:

if I am a purchaser, and I need to source for a certain item, then I look up the item and want to see all the vendors that are selling this item. We do have several sources:

* we did a price enquiry to which the potential vendor responded

* we did a recent purchase with that vendor, and thus have a recent purchase invoice available

Now, how does this work in SAP? Where is the screen to see all this information, and fe. the purchase prices, where are they fetched from?

thanks to give me some insights in this process, or flowchart.

best regards, Maarten