Explore this snippet here.
An essential part of cleaning a new data source is deciding how to treat NULL values. The Postgres function COALESCE can help with replacing NULL values with something else:
with data as ( select * from (values (1, 'one'), (null, 'two'), (3, null) ) as data (num, str) ) select coalesce(num, -1) num, coalesce(str, 'I AM NULL') str from data
|3||I AM NULL|