MS SQL Update Trigger to Sync Tables

This is a complex trigger. This will update mission-critical business values. I want to divide this into two jobs. Proof (small) and then Finished work. If you have the experience to take this project, let me know price for initial proof, and price for finished version. I can send scripts to create the tables. Here is the table structure, trigger action, and initial proof of concept: TABLE 1 SalesReport_Day (160 fields, with about 20 that are calculated fields) Each row represents the total value for various metrics for a day and is updated multiple times an hour. I am only concerned with the first 11 fields for the test. TABLE 2 SalesReport_Week (Is identical to SalesReport_Day with the exception that it has 2 date range fields (DateStart: first day of the week) and (DateEnd: last day of the week) instead of a {day of the month} field. Each row represents the total value for the same metrics for a week. It is the aggregate of the daily values from SalesReport_Day for a week. It is not updated by code. It will be updated by a trigger only. TRIGGER ACTION Initial concept (wrong-will not work): When a value in Table1 (SalesReport_Day ) is updated, the trigger needs to update (increment) the same column in Table2 (SalesReport_Week) with the amount of the change. The problem is that Table2 does not know how much the value in Table1 was increase/decreased. It cannot just add the field value from Table1 to the corresponding field in Table2 because after the first update, it would be adding values already added. Desired concept (I think this will work): Typically, only 1-3 fields in Table1 will be updated as a time. 1) The Table1 fields being updated and their original pre-update values need to be read to variables. 2) Then compare the new values to the pre-update values to get +- value (net change). 3) Then update Table2 with the net change values. One other thing that adds slightly to the complexity is that the trigger must first check to see if a row for the week already exists in Table2 (SalesReport_Week). If so then update. If not them insert the new row with the new DateStart and DateEnd values. All fields are defined with default values to make the insert simple. PROOF OF CONCEPT I only need you to do the trigger for the first 11 fields just to confirm we can get it to work as expected. FULL VERSION Once the Proof of Concept is complete, I want to create the full working version which will update all non-calculated fields in SalesReport_Week AND an additional table,SalesReport_Month (Table 3), which is not part of the first test. PURPOSE 1) Provide faster reporting and save resources by having data aggregated in the tables instead of a query. 2) Insure data across those tables representing multiple time frames is always in sync. OTHER I would be interested in your thoughts if using EntityFramework 6 vs SQL command would make any difference in the original code update that targets Table1. To be exact, I am wondering if the EF SQL output will make it clear which values are being updated (in creating the pre-update variables). Obviously, I don't want to read all 150+ fields into variables for each update. Just the ones being changed.