If you want to collect your regularly loaded data without overwriting it or create a load log that writes the load activites with a timestamp into a table, you need to create a query that adds new lines to it’s own latest version.
In both cases you add a column that returns the current day and time using DateTime.LocalNow()
Load Log the PowerBI-way
Then using Power BI it’s fairly easy: Use the R-extension to perform an append query to the external txt or csv-file like described in this post (incremental load):
write.table(trim(dataset), file=”your filepath & filename.txt”, sep = “\t”, row.names = FALSE, append = TRUE, column.names=FALSE)
Load Log the Power Query-way
In Excel’s Power Query it’s a bit trickier, because you cannot export your queries and therefore need to create the consolidated table in your workbook itself. And it must be a self-referencing query or to be more precise: a self-sourcing query: A query that takes its latest output as its new input, then appends the new data and overwrites the old result with the new one.
How do we deal with this? When we write the query we don’t have the result yet to be referenced?