Question

我有这个问题：

SELECT 
    pupils.id_pupil
  , name
  , surname
  , (select round(avg(qualifications.calificacion),2) from qualifications where id_pupil = pupils.id_pupil and qualifications.id_trimester=incidents.id_trimester and type_qualification='class') as media
  , (select count(calificacion) from qualifications where id_pupil = pupils.id_pupil and qualifications.id_trimester=incidents.id_trimester and type_qualification='class') as count
  , COALESCE(sum(type_incident='miss' and level=1 and class='A' and id_trimester=1),0) as misses
  , COALESCE(sum(type_incident='delay' and level=1 and class='A' and id_trimester=1),0) as delays
  , COALESCE(sum(type_incident='attitude' and level=1 and class='A' and id_trimester=1),0) as attitude
  , COALESCE(sum(type_incident='miss_justif' and level=1 and class='A' and id_trimester=1),0) as misses_justificadas 
FROM 
    pupils 
    left join incidents         ON incidents.id_pupil=pupils.id_pupil
WHERE 
    level=1
    and class='A' 
    and id_trimester=1 
GROUP BY id_pupil

表：

pupils: (id_pupil, name, surname, email, user, pass, level, class)
incidents: (id_incidents, date, time, type_incident, comments, id_pupil, id_user, subject, id_trimester)
qualifications: (id_qualification, qualification, date, time, subject, id_pupil, id_user, id_trimester, type_qualification)

它有效，但它没有显示带有未命中，延迟，态度和misses_justif的行，其中四个值为0.该行被省略。

如何显示所有行？

谢谢！

Answer 1

您的查询存在一些问题。我做了一个修改，也许你给了你想要的结果。也许你应该把名字和姓氏，媒体和计数值放在你的组中，但这取决于你，因为它取决于你的要求。

SELECT 
 pupils.id_pupil
 , name
 , surname
 , IFNULL(qua.media, 0) media
 , IFNULL(qua.count, 0) count
 , sum( case when type_incident='miss' then 1 else 0 end ) as misses
 , sum( case when type_incident='delay' then 1 else 0 end ) as delays
 , sum( case when type_incident='attitude' then 1 else 0 end ) as attitude
 , sum( case when type_incident='miss_justif' then 1 else 0 end ) 
 as misses_justificadas 
FROM 
 pupils 
 LEFT JOIN incidents ON incidents.id_pupil=pupils.id_pupil
 LEFT JOIN
 (select id_pupil, id_trimester, 
 count(qualification) count, 
 round(avg(qualifications.qualification),2) media
 from qualifications 
 where type_qualification='class'
 group by id_pupil, id_trimester ) as qua
 ON ( qua.id_pupil = pupils.id_pupil )
WHERE 
 level=1
 and class='A' 
 and qua.id_trimester=1 
GROUP BY pupils.id_pupil

在MYSQL Query和左连接上显示空值

1 个答案: