HAVING COUNT condition doesn't work

Question

$rech=$_bdd->query('select distinct num_carte,type_seance,nom_module from absence,seance,absence_justification,module where absence.id_absence=absence_justification.id_absence AND absence.id_seance=seance.id_seance AND seance.id_module=module.id_module GROUP BY num_carte,type_seance,nom_module having count(jus_admin="non")>4 ');

I have this code in my PHP website and when I use the having count , I found that the count doesn't compare jus_admin="non" . It ignore the condition so he just count the number of jus_admin and return the result I didn't understand why he ignore the condition !!!!!!!

Answer 1

count() counts the number of non-NULL values. Booleans in MySQL are typically 0 or 1.

So, your logic:

having count(jus_admin = 'non') > 4

only returns NULL if jus_admin is NULL . This is equivalent to:

having count(jus_admin) > 4

Which, if it never takes on NULL , would be the same as:

having count(*) > 4

I think you want sum() rather than count() :

having sum(jus_admin = 'non') > 4

This will require at least five 'non' values for each group that is returned.