How to generate date series to occupy absent dates in google BiqQuery?

Question

I am trying to get daily sum of sales from a google big-query table. I used following code for that.

select Day(InvoiceDate) date, Sum(InvoiceAmount) sales f         


        

Answer 1

Generting a list of dates and then joining whatever table you need on top seems the easiest. I used the generate_date_array + unnest and it looks quite clean.

To generate a list of days (one day per row):

  SELECT
  *
  FROM 
    UNNEST(GENERATE_DATE_ARRAY('2018-10-01', '2020-09-30', INTERVAL 1 DAY)) AS example