[postgresql] PostgreSQL 'NOT IN' and subquery

I'm trying to execute this query:

SELECT mac, creation_date 
FROM logs 
WHERE logs_type_id=11
AND mac NOT IN (select consols.mac from consols)

But I get no results. I tested it, and I know that there is something wrong with the syntax. In MySQL such a query works perfectly. I've added a row to be sure that there is one mac which does not exist in the consols table, but still it isn't giving any results.

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
  );

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.