Replace NULL values

Replace NULLs

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Description

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
num str
1 a
-1 b
3 I AM NULL
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