Good day,

I am in the process of migrating a Qlikview report into Power BI. I have not encountered the previous() function before. I am attempting the same result with a SQL LAG() function, but this is simply not working for me as I understand it.

The Qlikview function is as follows:

LOAD
if(sourceid = previous(sourceid) and serviceid = previous(serviceid),interval(rdate - previous(timestamp(rdate)),'D'),0) as days_interval
resident dialed
order by source_id, rdate, load_id

I have attemptred the following BigQuery script, but with no luck. Perhaps I am missing something in the Qlikview logic that isn’t the same as LAG()?

IF(
   dialed.source_id = LAG(dialed.source_id) OVER (ORDER BY dialed.rdate) AND dialed.service_id = LAG(dialed.service_id) OVER (ORDER BY dialed.rdate),
   TIMESTAMP_DIFF(dialed.rdate, LAG(dialed.rdate) OVER (ORDER BY dialed.rdate), DAY),
   0
  )

Is anyone familiar with the previous() function, and perhaps a better way to code it up in BigQuery?