Strangely beautiful SQL UPDATE (PostgreSQL 12)

When you need to fill data to null fields of multiple records, you had better avoid UPDATE. Rather:

1. Prepare for a table to insert all the data to fill
2. Use SELECT ~ OUTER JOIN to join with the original table
3. And prepare for the "result" table to push the JOINed results via INSERT INTO.
   

I found out that I could finish the job in 5:35 when traditional UPDATE didn't finish in 10 minutes.

Tested under PostgreSQL 12.