Subtract two layers based on attributes

Discussion created by dynamike on Jan 23, 2012
Hello. I need help about this:
I have three layers. The first contains parcels of a town, the second - the old planning zones of the town and the third - the new planning zones of the town.
Now i want to know which parcels have changed planning zone and which. Take in mind that a parcel might be crossed with more than one planning zone.
What i have done so far, is to make some test with the analysis tools and i concluded that the best tool for my first step of analysis, is the intersection tool. So now i have two layers, that are the product of the intersection of the first layer (parcels) with the other two (planning zones old & new) respectively.
Is there any way that i can substract those two layers spatially but based on an attribute (for example planning zone code)? Because now after the intersection, some parcels have the same spatial limits but different zone. Some other, after the intersection, although in reality are the same polygon, now are two different rows because they were crossed by two planning zones.
Any ideas how to work from here or from the start?