Bigquery Table Lead Column Values Based On Date - mysql

Question

I want to duplicate a (revenue) column and shift it one year in order to make YoY comparisons. Currently looking to lead values in a Big Query table based on a specific date to achieve this but stuck.
I used DATE_ADD to create a new column to get the date of last year but now I want to get a column next to it with the revenue based on the DATE_ADD date.
One problem is that not all locations include the same date, that's why it's harder to make the shift.
There is no way to properly format a table so I have an image of the intended result here. Where basically the revenue_last_year should fill in with the value of the revenue column corresponding to the date_add column and the right location.
The query below is as far as I've been able to go:
SELECT
Date,
location,
revenue,
DATE_ADD(date, INTERVAL -1 YEAR) AS DateAdd,
LEAD(revenue, ##OFFSET## ) OVER (PARTITION BY location ORDER BY date DESC) AS revenue_last_year
FROM
`dataset.table1`
Does anyone have a suggestion on how to relate the offset value to the right date? Or should I approach this in a completely different way?

Answer 1

Below is for BigQuery Standard SQL
#standardSQL
SELECT
a.date, a.location, a.revenue,
DATE_SUB(a.date, INTERVAL 1 YEAR) date_last_year,
IFNULL(b.revenue, 0) revenue_last_year
FROM `project.dataset.table` a
LEFT JOIN `project.dataset.table` b
ON a.location = b.location
AND DATE_SUB(a.date, INTERVAL 1 YEAR) = b.date
You can test, play with above using dummy data as in below example
#standardSQL
WITH `project.dataset.table` AS (
SELECT DATE '2018-02-20' `date`, 'A' location, 1 revenue UNION ALL
SELECT '2018-02-20', 'B', 2 UNION ALL
SELECT '2018-02-21', 'A', 3 UNION ALL
SELECT '2018-02-22', 'B', 4 UNION ALL
SELECT '2019-02-20', 'A', 5 UNION ALL
SELECT '2019-02-20', 'B', 6 UNION ALL
SELECT '2019-02-21', 'A', 7 UNION ALL
SELECT '2019-02-21', 'B', 8 UNION ALL
SELECT '2019-02-22', 'A', 9 UNION ALL
SELECT '2019-02-22', 'B', 10
)
SELECT
a.date, a.location, a.revenue,
DATE_SUB(a.date, INTERVAL 1 YEAR) date_last_year,
IFNULL(b.revenue, 0) revenue_last_year
FROM `project.dataset.table` a
LEFT JOIN `project.dataset.table` b
ON a.location = b.location
AND DATE_SUB(a.date, INTERVAL 1 YEAR) = b.date
-- ORDER BY a.date, a.location
with result
Row date location revenue date_last_year revenue_last_year
1 2018-02-20 A 1 2017-02-20 0
2 2018-02-20 B 2 2017-02-20 0
3 2018-02-21 A 3 2017-02-21 0
4 2018-02-22 B 4 2017-02-22 0
5 2019-02-20 A 5 2018-02-20 1
6 2019-02-20 B 6 2018-02-20 2
7 2019-02-21 A 7 2018-02-21 3
8 2019-02-21 B 8 2018-02-21 0
9 2019-02-22 A 9 2018-02-22 0
10 2019-02-22 B 10 2018-02-22 4