在OLTP系统中实现行版本控制的DataModel

Question

I have following table

• Person(PID, Name, Dob, AddressId) PID being surrogate key(auto incremented)

• Address(AddressId, Line1, Line2, City, State) AddressId being surrogate key(auto incremented)

PersonID (PID) is used in my lot of transaction tables. Since address of a person may change over the period of time, I need to store record version in database so that I can refer correct version according to time slice. How should I handle it.

I am thinking of having solution something like this

• Using same table to store history eg
• Person(PID, Name, Dob, AddressId)
• Address(AddressId, Line1, Line2, City, State, StartDate, EndDate, LastUpdatedBy, LastUpdatedDate)

Let's assume initial record of person as below

Person(100, X, Y, 110)
Address(110, A, B, C, D, 2011-01-01, 9999-12-31, Y, 2011-01-01)

Now address was changed in 2012 for PID 100. I am thinking to do

Address(320, A, B, C, D, 2011-01-01, 2012-06-01, Y, 2011-01-01) - INSERT
Address(110, A, B, Q, D, 2012-06-01, 9999-12-31, Z, 2012-06-01) - UPDATE

if address changes again in 2014 for PID 100. It would look like

Address(740, A, B, Q, D, 2012-06-01, 2014-06-01, Y, 2012-01-01) - INSERT
Address(320, A, B, C, D, 2011-01-01, 2012-06-01, Y, 2011-01-01) - NO CHANGE
Address(110, A, B, N, D, 2014-06-01, 9999-12-31, R, 2012-06-01) - UPDATE

Now I can query historical data as well as current data from same table without changing surrogate key. I won't have to refer historical tables hence no bombarding of logic and tables.

This approach won't let me enforce unique key constraint on tables assuming I have Address Code being unique. How shall I handle this?

Please suggest different approach and feedback on this.

Answer 1

What I would do is to make a relation table that contains dates:

Person_At_Address(PID,AddressId,StartDate,EndDate,LastUpdatedBy,LastUpdatedDate)

And remove the corresponding columns from Person and Address yielding:

Person(PID, Name, Dob)
Address(AddressId, Line1, Line2, City, State)

Now whenever a person changes the address you just insert a new row into the Person_At_Address table. When querying, you have got all the info you need about historic and current data.

As for your case with NO-CHANGE row, you have number of options to pull it out:

• You can have a scheduled job that inserts rows at given checkpoints in time if there is no row present for that time slice. Then select query gives you exactly the above output.
• You can also create a display like that after you run the query by filling in the missing rows in your application. That is fairly simple also.