PostgreSQL 'NOT IN' and subquery

When using NOT IN you should ensure that none of the values are NULL:

SELECT mac, creation_date 
FROM logs 
WHERE logs_type_id=11
AND mac NOT IN (
    SELECT mac
    FROM consols
    WHERE mac IS NOT NULL -- add this
)

You could also use a LEFT JOIN and IS NULL condition:

SELECT 
  mac, 
  creation_date 
FROM 
  logs
    LEFT JOIN consols ON logs.mac = consols.mac
WHERE 
  logs_type_id=11
AND
  consols.mac IS NULL;

An index on the "mac" columns might improve performance.

When using NOT IN, you should also consider NOT EXISTS, which handles the null cases silently. See also PostgreSQL Wiki

SELECT mac, creation_date 
FROM logs lo
WHERE logs_type_id=11
AND NOT EXISTS (
  SELECT *
  FROM consols nx
  WHERE nx.mac = lo.mac
  );

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