How to query MySQL to count NULL values in database field?

Question

How to query MySQL to count 'NULL' values in database table column. My query in response always 0 print.

$rawm_jan_full=Yii::app()->db->createCommand("SELECT COUNT(trainings_id) AS trail_list from children WHERE MONTH(timestamp) = '1' AND YEAR(timestamp) ='".$previous_year."' AND trainings_id IS NULL ")->queryRow();

print_r($rawm_jan_full);

Answer 1

$rawm_jan_full=Yii::app()->db->createCommand("SELECT COUNT(case when trainings_id is null then 1 else trainings_id end ) AS trail_list from children WHERE MONTH(timestamp) = '1' AND YEAR(timestamp) ='".$previous_year."' AND trainings_id IS NULL ")->queryRow();

 Replace COUNT(trainings_id )  with    COUNT(case when trainings_id is null then 1 else trainings_id end ) in order to include null in your count result