Index,match, vlookup?
 

This seems to be my day for questions.

Within a workbook I have a worksheet of (all) purchase order numbers. Each
PO has one or more line items (identified numberically). Each line item has
a corresponding department number. These would be columns A, B & C and
contains about 9,000 rows (and counting).

I have a second worksheet that has just PO number and line number columns A
& B(plus cost & unit data that I am trying to analyze).

What formula can I use that will match the PO & line item number in the
second sheet to the corresponding PO & line item number in the first sheet
and bring over the department number?

I have looked on CPearson.com but do not see (or understand how to adapt) a
formula to my need.

It would be easier if I could get all the data I need on one worksheet, but
the way our corporate database is set up, I can only get pieces.

Thanks,

Ron R.