In product development we keep bill of materials (BOM) with cost information. I upload the current BOM every week. These BOMs are aggrageted in a querry wich returns a table of BOMs appended together with a date column. So one can see the cost of a particular BOM at a certain date. Below shows part of the table.
What I want to achieve is to select two particular dates and see the changes in column 'functions', such electrical (EL), mechanical (ME), packaging (PKG). The purpose is to see what was the assumption for PKG back then and what is it now. I need a table that returns only those items that are different in that particular category. It is all about change traking. Because cost increases or decreases in a development happens, but taking necessary actions is the key. Without knowing what is causing the change, one can't tackle the problem. Can anyone help me with how to go about this issue?