Any particular reason or use-case you are doing this? BigQuery stores data in columns, so adding more columns is often not the best solution. Other applications that read your data (Looker, Tableau, Excel, Python, R) can often handle pivoting in a much easier fashion.
– rtenhaFeb 20 '20 at 20:45
Closing because Mikhail's answer linked in the question is one of the best available answers for this problem for now.
– Felipe HoffaFeb 20 '20 at 22:03