How to UNNEST multiple arrays in BigQuery standardSQL

Question

I am selecting data from Google Bigquery table which includes JSON column. My table has multiple nested arrays, one of the includes two nested levels. here is my table schema

https://imgur.com/UBPKUMx

My statement is:

SELECT 
items.*,
pay.*,
credits.creditnoteid,
credits.id,
credits.total
FROM client_account.invoices,
UNNEST(lineitems) items,
UNNEST(items.tracking),
UNNEST(payments) pay,
UNNEST(creditnotes) credits

https://imgur.com/c1YT258

Unfortunately I get no results... Can you help me to unnest all of the arrays.

Answer 1

Ok, I did a test on one of my datasets. I think that creditnotes is always null . Because in my case I get no results when I unnest a column that is always null. You can fix it by using LEFT JOIN I modified your query to use left joins but you might be able to tune it better.

SELECT 
items.*,
tracking.*,
pay.*,
credits.creditnoteid,
credits.id,
credits.total
FROM client_account.invoices
LEFT JOIN UNNEST(lineitems) items
LEFT JOIN UNNEST(items.tracking) tracking
LEFT JOIN UNNEST(payments) pay
LEFT JOIN UNNEST(creditnotes) credits