Iterate through table by date column for each common value of different column - sql

Question

Below I have the following table structure:
CREATE TABLE StandardTable
(
RecordId varchar(50),
Balance float,
Payment float,
ProcDate date,
RecordIdCreationDate date,
-- multiple other columns used for calculations
)
And here is what a small sample of what my data might look like:
RecordId Balance Payment ProcDate RecordIdCreationDate
1 1000 100 2005-01-01 2005-01-01
2 5000 250 2008-01-01 2008-01-01
3 7500 350 2006-06-01 2006-06-01
1 900 100 2005-02-01 NULL
2 4750 250 2008-02-01 NULL
3 7150 350 2006-07-01 NULL
The table holds data on a transactional basis and has millions of rows in it. The ProcDate field indicates the month that each transaction is being processed. Regardless of when the transaction occurs throughout the month, the ProcDate field is hard coded to the first of the month that the transaction happened in. So if a transaction occurred on 2009-01-17, the ProcDate field would be 2009-01-01. I'm dealing with historical data, and it goes back to as early as 2005-01-01. There are multiple instances of each RecordId in the table. A RecordId will show up in each month until the Balance column reaches 0. Some RecordId's originate in the month the data starts (where ProcDate is 2005-01-01) and others don't originate until a later date. The RecordIdCreationDate field represents the date where the RecordId was originated. So that row has millions of NULL values in the table because every month that each RecordId didn't originate in is equal to NULL.
I need to somehow look at each RecordId, and run a number of different calculations on a month to month basis. What I mean is I have to compare column values for each RecordId where the ProcDate might be something like 2008-01-01, and compare those values to the same column values where the ProcDate would be 2008-02-01. Then after I run my calculations for the RecordId in that month, I have to compare values from 2008-02-01 to values in 2008-03-01 and run my calculations again, etc. I'm thinking that I can do this all within one big WHILE loop, but I'm not entirely sure what that would look like.
The first thing I did was create another table in my database that had the same table design as my StandardTable and I called it ProcTable. In that ProcTable, I inserted all of the data where the RecordIdCreationDate was not equal to NULL. This gave me the first instance of each RecordId in the database. I was able to run my calculations for the first month successfully, but where I'm struggling is how I use the column values in the ProcTable, and compare those to the column values where the ProcDate is the month after that. Even if I could somehow do that, I'm not sure how I would repeat that process to compare the 2nd month's data to the 3rd month's data, and the 3rd month's data to the 4th month's data, etc.
Any suggestions? Thanks in advance.

Answer 1

Seems to me, all you need to do is JOIN the table to itself, on this condition
ON MyTable1.RecordId = MyTable2.RecordId
AND MyTable1.ProcDate = DATEADD(month, -1, MyTable2.ProcDate)
Then you will have all the rows in your table (MyTable1), joined to the same RecordId's row from the next month (MyTable2).
And in each row you can do whatever calculations you want between the two joined tables.