Django JOIN。選擇數據+ SELECT COUNT

Question

有兩種型號：

class KeywordCategory(models.Model): 
    class Meta(): 
     db_table = 'keywords_category' 
    category_name = models.CharField(max_length = 100) 
... 
class Keyword(models.Model): 
    class Meta(): 
     db_table = 'keywords' 
    keyword_category = models.ForeignKey(KeywordCategory) 
    keyword_text  = models.CharField(max_length = 100) 

我需要得到所有的類別和它們的條目數。

SQL語法：

SELECT keywords_category.*, COUNT(keywords.id) as count_keywords 
FROM keywords_category 
LEFT JOIN keywords ON keywords_category.id=keywords.keyword_category_id 
GROUP by keywords_category.id 

Answer 1

這將返回一個字典和鍵將是keyword_category和total。

from django.db.models import Count 

kw_counts = Keyword.objects.all().values('keyword_category').annotate(
    total=Count('keyword_category') 
) 

Answer 2

獲取所有類別：

categories = KeywordCategory.objects.all() 

計數的條目在其中：

for category in categories: 
    category.keyword_set.count() 

Answer 3

keywords = KeywordCategory.objects.all() 

print [(k, k.keyword_set.count()) for k in keywords]