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

Using the Standard SQL dialect and the generate_array function to simplify the code:

WITH serialnum AS (
  SELECT
    sn
  FROM
    UNNEST(GENERATE_ARRAY(0, 
                          DATE_DIFF(DATE_ADD(DATE_TRUNC(CURRENT_DATE()
                                                      , MONTH)
                                          , INTERVAL 1 MONTH)
                                  , DATE_TRUNC(CURRENT_DATE(), MONTH)
                                  , DAY) - 1)
                          ) AS sn
), date_seq AS (
SELECT
    DATE_ADD(DATE_TRUNC(CURRENT_DATE(), MONTH),
            INTERVAL(sn) DAY) AS this_day
FROM
  serialnum
)
SELECT
    Day(InvoiceDate) date
    , Sum(IFNULL(InvoiceAmount, 0)) sales
FROM
    date_seq
    LEFT JOIN
    test_gmail_com.sales
ON
    date_seq.this_day = DAY(test_gmail_com.sales.InvoiceDate)
WHERE
    year(InvoiceDate) = Year(current_date())
    and
    Month(InvoiceDate) = Month(current_date())
GROUP BY
    date
ORDER BY
    date
;

UPDATE

Or, simpler still using the generate_date_array function:

WITH date_seq AS (
SELECT
  GENERATE_DATE_ARRAY(DATE_TRUNC(CURRENT_DATE(), MONTH), 
                      DATE_ADD(DATE_ADD(DATE_TRUNC(CURRENT_DATE(), MONTH)
                                        , INTERVAL 1 MONTH)
                               , INTERVAL -1 DAY)
                      , INTERVAL 1 DAY)
    AS this_day
)
SELECT
    Day(InvoiceDate) date
    , Sum(IFNULL(InvoiceAmount, 0)) sales
FROM
    date_seq
    LEFT JOIN
    test_gmail_com.sales
ON
    date_seq.this_day = DAY(test_gmail_com.sales.InvoiceDate)
WHERE
    year(InvoiceDate) = Year(current_date())
    and
    Month(InvoiceDate) = Month(current_date())
GROUP BY
    date
ORDER BY
    date
;