Django查询：Count和Group BY [英] Django query: Count and Group BY

问题描述

我有一个查询，我试图想出django的方式：
我想从Call调用最后100个呼叫。这很容易：
call = Call.objects.all（）。order_by（' - call_time'）[：100]

然而下一部分我可以找不到通过django的ORM做的方式。我想获得一个call_types的列表和每个人在之前的queryset我刚刚做的呼叫数。通常我会这样查询：SELECT COUNT（id），calltype FROM call WHERE id IN（SELECT id FROM call ORDER BY call_time DESC LIMIT 100）GROUP BY calltype;

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这是我的2个模型：

  class Call（models.Model）：
 call_time = models.DateTimeField（Call Time，auto_now = False，auto_now_add = False）
 description = models.CharField（max_length = 150）
 response = models.CharField（max_length = 50）
 event_num = models.CharField（max_length = 20）
 report_num = models.CharField（max_length = 20）
 address = models.CharField（max_length = 150）
 zip_code = models.CharField（max_length = 10）
 geom = models.PointField（srid = 4326）
 calltype = models.ForeignKey（CallType）
 
 objects = models.GeoManager（）
 
 class CallType（models.Model）：
 name = models.CharFi eld（max_length = 50）
 description = models.CharField（max_length = 150）
 active = models.BooleanField（）
 time_init = models.DateTimeField（Date Added，auto_now = False， auto_now_add = True）
 
 objects = models.Manager（）
  

解决方案

尝试这样：

  calls = Call.objects.all（）。order_by（' -  call_time '）[：100] 
 types = CallType.objects.filter（call__in = calls）.annotate（Count（'call'））
  

您可能需要向后一个查询器添加distinct（）。

I have a query that I'm trying to figure the "django" way of doing it: I want to take the last 100 calls from Call. Which is easy: calls = Call.objects.all().order_by('-call_time')[:100]

However the next part I can't find the way to do it via django's ORM. I want to get a list of the call_types and the number of calls each one has WITHIN that previous queryset i just did. Normally i would do a query like this: "SELECT COUNT(id),calltype FROM call WHERE id IN ( SELECT id FROM call ORDER BY call_time DESC LIMIT 100 ) GROUP BY calltype;"

I can't seem to find the django way of doing this particular query.

Here are my 2 models:

class Call( models.Model ):
    call_time = models.DateTimeField( "Call Time", auto_now = False, auto_now_add = False )
    description = models.CharField( max_length = 150 )
    response = models.CharField( max_length = 50 )
    event_num = models.CharField( max_length = 20 )
    report_num = models.CharField( max_length = 20 )
    address = models.CharField( max_length = 150 )
    zip_code = models.CharField( max_length = 10 )
    geom = models.PointField(srid=4326)
    calltype = models.ForeignKey(CallType)

    objects = models.GeoManager()

class CallType( models.Model ):
    name = models.CharField( max_length = 50 )
    description = models.CharField( max_length = 150 )
    active = models.BooleanField()
    time_init = models.DateTimeField( "Date Added", auto_now = False, auto_now_add = True )

    objects = models.Manager()

解决方案

try this:

calls = Call.objects.all().order_by('-call_time')[:100]
types = CallType.objects.filter(call__in=calls).annotate(Count('call'))

you might need to add distinct() to the latter queryset though.

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