Newbie Question about Groups and sums

It's quite possible that you do not need the second table at all. You can generate a summary report with one row of data for every unique value of Field1 with a sub total placed next to it. See this thread for a tutorial on summary reports: Creating Filemaker Pro summary reports--Tutorial

But you can also define a table where field 1 is the date shown and used as a match field to set up a relationship in Manage | database | relationships linking the two tables by date:

Table1::DateField = Table2::DateField

Then Table2::field2 can be defined as a calculation field: Sum ( Table1::Field2 ) to compute the total.

It is also possible to set up calculation fields that use ExecuteSQL to compute such a an aggregate value.

What you describe does not sound like reasons to have the second table. Your other calcs might possibly be done as part of your summary report design and if you have to export this data for the "external charting engine", you can export the summarized data such that you get one row of exported data per date just as you would have in your summary report.

There are many ways to populate such a table. Here's just one:

Define your relationship to match by date fields, but also double click the relationship line and select "allow creation of records via this relationship" for the second table.

Then this script step, performed from each record of the original table:

Set Field [Table2::DateField ; Table1::DateField ]

Will create new records in Table2 without creating any duplicate records. Please note, however, that you may need to take additional steps to handle situations where a record in Table1 is deleted or the date is modified to be a new date, leaving an "orphan" record in Table2.