UPDATE:

Just to mention it on a more visible place. When I changed IN for =, the query execution time went from 180 down to 0.00008 seconds. Ridiculous speed difference.

This SQL query takes 180 seconds to finish! How is that possible? is there a way to optimize it to be faster?

SELECT IdLawVersionValidFrom 
FROM question_law_version 
WHERE IdQuestionLawVersion IN 
  (
  SELECT MAX(IdQuestionLawVersion) 
  FROM question_law_version 
  WHERE IdQuestionLaw IN 
    (
    SELECT MIN(IdQuestionLaw) 
    FROM question_law 
    WHERE IdQuestion=236 AND IdQuestionLaw>63
    )
  )

There are only about 5000 rows in each table so it shouldn't be so slow.

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