I think this interactive flow should work:
I have two tables, this small table determines the columns I wish to keep
My other table has much more data but I need to just get those columns
you can use Join to basically overwrite the values is smaller table
With pure script solution it could look something like this. First get the column names from the smaller table into a list using << Get Column Names("String") and then use that list in << Subset()
Names Default To Here(1);
dtbig = Open("$SAMPLE_DATA/Big Class Families.jmp");
dtsmall = Open("$SAMPLE_DATA/Big Class.jmp");
cols_to_keep = dtsmall << Get Column Names("String");
dt_new = dtbig << Subset(All Rows, Columns(cols_to_keep));
-Jarmo