Well, this sounds very complex, but I will try to give a couple of examples
that might help you out.
The way I understand it each property would have some kind of identifying
number that never changes and some data that never changes. I am looking at
the Harris County (
www.HCAD.ORG) for an example. Here is what I might do
for the main table...
TblPropertyMain
PropertyAccountNumber
ClassCode
LandUseCode
LandArea
Legal DescriptionLot
Legal DescriptionBlock
LegalDescriptionNeighborhood
LegalDescriptionSection
PropertyAddress1
PropertyAddress2
PropertyCity
PropertyState
PropertyZIP
That's about it!
Now, each property can have one (or more) improvements on it. I guess you
even have some tht have no improvements. This means you have a one-to-many
relationship. We need a new table for Improvements that is somehow related
to the Property. Maybe something like this...
TblImprovements
UniqueImprovementNumber
PropertyAccountNumber
ImprovementDescription
ImprovementSiteCode
ImprovementSquareFootage
etc.
Okay, now each property has an owner. Some owners have more than one
property. You need a table that stores each owner.
TblTaxPayer
UniqueOwnerNumber (SS#?)
OwnerLastName
OwnerFirstName
OwnerMiddle
OwnerSuffix
OwnerMailingAddress1
OwnerMailingAddress2
OwnerMailingCity
OwnerMailingState
OwnerMailingZIP
OwnerPhone
etc.
But, now you have to tie owners to properties. This requires a junction
table. You also need to know if they still own the property, so you may
need to include purchase dates.
TblPropertiesAndOwners
UniqueOwnerNumber
PropertyAccountNumber
DatePurchased
DateSold
This does not even get into the appraised values. Since they change each
year and you need to track history, you will have to create a table and make
a SEPARATE entry for each year that the property is appraised. You might
have to break this down into taxing authorites. This MIGHT look something
like...
TblAppraisalDetails
PropertyAccountNumber
AppraisalDate
TaxingAuthorityNumber (Probably need another table with the
numbers and the associated names)
Rate
AppraisedValue
ExemptAmount
etc.
Be careful not to do any math here. You don't need to store the total
value, the exempt amount, and the taxable amount. You can calcualte the
taxable amount using the other two values. Don't store the total tax. You
can calculate this by multiplying the TaxableAmount by the Rate. No need to
store the total.
As you can see, you have a very very complex puzzle ahead of you. I'd
recommend you sit down and map this out on paper before you start building
tables. You might also read up on normalization and relationships. My
guess would be that you have a situation that would really benefit from
paying a professional to come in and get you started. If you pay a pro for
a couple of weeks or a month, they could get your structure built and even
create some basic forms, reports, and queries.