SQL from QTD to daily values bigquery - sql

Question

We receive QTD data daily, what is needed is to transform it to daily -or even monthly any one would work-
The value column has no particular pattern it can increase and decrease and might reach to zero because of the product returns and might be the same value -no purchase- or missing for any other reason
SKU
value
Date
ABC
200
2022-01-10
ABC
300
2022-02-10
ABC
100
2022-03-10
XYZ
1000
2022-01-10
XYZ
1200
2022-02-10
XYZ
2022-03-10
Now the required out put should be like this, also avoiding a new quarter value to get subtracted from last day of the previous quarter value
SKU
value
Date
ABC
200
2022-01-10
ABC
100
2022-02-10
ABC
-200
2022-03-10
XYZ
1000
2022-01-10
XYZ
200
2022-02-10
XYZ
0
2022-03-10
The tricky part would be in the entry of the new quarter for example
assuming by default that Q4 is from October to December and Q1 from Jan to March
SKU
value
Date
ABC
200
2022-01-12
ABC
300
2022-02-12
ABC
100
2022-03-12
ABC
100
2022-01-01
ABC
250
2022-02-01
ABC
300
2022-03-01
This should be
SKU
value
Date
ABC
200
2022-01-12
ABC
100
2022-02-12
ABC
-200
2022-03-12
ABC
100
2022-01-01
ABC
150
2022-02-01
ABC
50
2022-03-01
This is on big query any help would be much appreciated

Answer 1

You might consider below.
WITH sample_table AS (
SELECT 'ABC' SKU, 200 value, '2022-01-12' Date UNION ALL
SELECT 'ABC' SKU, 300 value, '2022-02-12' Date UNION ALL
SELECT 'ABC' SKU, 100 value, '2022-03-12' Date UNION ALL
SELECT 'ABC' SKU, 100 value, '2022-01-01' Date UNION ALL
SELECT 'ABC' SKU, 250 value, '2022-02-01' Date UNION ALL
SELECT 'ABC' SKU, 300 value, '2022-03-01' Date
)
SELECT SKU,
IFNULL(value - LAG(value, 1, 0) OVER w, 0) AS value,
Date
FROM (SELECT * REPLACE(PARSE_DATE('%Y-%d-%m', Date) AS Date) FROM sample_table)
WINDOW w AS (PARTITION BY SKU, EXTRACT(YEAR FROM Date), EXTRACT(QUARTER FROM Date)
ORDER BY UNIX_DATE(Date));
Query results