从表字段中选择不同的值 [英] Select distinct values from a table field
问题描述
SELECT DISTINCT myfieldname FROM mytable
(或者)
SELECT myfieldname FROM mytable GROUP BY myfieldname
我至少喜欢在使用原始sql之前做Django方式。
例如,一个表:
id,街道,城市
1,主街,赫尔
2,其他街,Hull
3,Bibble Way,莱斯特
4,莱斯特的另一种方式
5,High Street,Londidium
我想得到:
Hull,Leicester,Londidium
说你的模型是店铺
class Shop(models.Model):
street = models.CharField(max_length = 150)
city = models.CharField(max_length = 150 )
#你的某些模型可能有明确的订单
class Meta:
ordering =('city')
由于您可能有 Meta
类订购
属性设置,您可以使用 order_by()
而无需清除任何参数使用 distinct()
时的排序。请参阅 order_by
()
如果您不希望将任何顺序应用于查询,默认排序,调用order_by(),不带参数。
和 distinct()
在其中讨论使用问题的注释
要查询您的数据库,您只需拨打:
models.Shop.objects.order_by()。values('city')。distinct()#返回字典
或
models.Shop .objects.order_by()。values_list('city')。distinct()#返回一个元组的列表。
您还可以将 flat = True
添加到 values_list
要有一个平面列表。
另请参见:按字段获取不同的Queryset值
I'm struggling getting my head around the Django's ORM. What I want to do is get a list of distinct values within a field on my table .... the equivalent of one of the following:
SELECT DISTINCT myfieldname FROM mytable
(or alternatively)
SELECT myfieldname FROM mytable GROUP BY myfieldname
I'd at least like to do it the Django way before resorting to raw sql. For example, with a table:
id, street, city
1, Main Street, Hull
2, Other Street, Hull
3, Bibble Way, Leicester
4, Another Way, Leicester
5, High Street, Londidium
I'd like to get:
Hull, Leicester, Londidium.
Say your model is 'Shop'
class Shop(models.Model):
street = models.CharField(max_length=150)
city = models.CharField(max_length=150)
# some of your models may have explicit ordering
class Meta:
ordering = ('city')
Since you may have the Meta
class ordering
attribute set, you can use order_by()
without parameters to clear any ordering when using distinct()
. See the documentation under order_by
()
If you don’t want any ordering to be applied to a query, not even the default ordering, call order_by() with no parameters.
and distinct()
in the note where it discusses issues with using distinct()
with ordering.
To query your DB, you just have to call:
models.Shop.objects.order_by().values('city').distinct() # returns a dictionary
or
models.Shop.objects.order_by().values_list('city').distinct() # returns a list of tuples.
You can also add flat=True
to values_list
to have a flat list.
See also: Get distinct values of Queryset by field
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