Find number of customers and orders and group by month (Bigquery)

Question

I need to get monthly sales numbers in each Country & region.

Also - a number of orders, customers and sales persons in each month with a total amount.

I got stuck as I cannot understand how to make all counts/sum and also group by month as I only have daily data.

I have tried something like this:

SELECT
orderdate,
  TerritoryID,
  (
  SELECT
    COUNT(SalesOrderID)
  FROM
    adwentureworks_db.salesorderheader),
  COUNT(DISTINCT CustomerID) SalesPersonID,
  SUM(totaldue)
FROM
  adwentureworks_db.salesorderheader
GROUP BY
  OrderDate,
  TerritoryID,
  TotalDue`

It should look like this:

Data:

Answer 1

The 1st day of a month can be obtained by date_trunc(orderdate,month)

For the inner SELECT , I do not know what you want to archive. The total number can be obtained by a window function count(...) over() .

Select 
 date_trunc(orderdate,month),
 TerritoryID,
 COUNT(DISTINCT CustomerID) as SalesPersonID,
 SUM(totaldue) as totaldue,
 COUNT(SalesOrderID) over () as totalsalesorder_of_whole_table
FROM adwentureworks_db.salesorderheader
GROUP BY 1,2