Django在查询集中切片单个字段 [英] Django slice a single field in a queryset
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问题描述
我试图从一个char字段中获取前五个字符,但对于查询集中的一个字段,却一直出现各种错误。在视图中是否有有效的方法?
I am trying to grab the first five characters from a char field but for only one field in a queryset but I keep getting various errors. Is there an effective way to do this in the view?
我正在尝试的代码:
var = Model.objects.values('field1', 'field2'[:5], 'field3')
推荐答案
You can annotate the queryset with first 5 letters of field2
using Substr
function:
from django.db.models.functions import Substr
queryset = Model.objects.all()
queryset = queryset.annotate(field2_5=Substr('field2', 1, 5))
,然后在值中使用带注释的字段 field2_5
:
And, then use the annotated field field2_5
in values:
values = queryset.values('field1', 'field2_5', 'field3')
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