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我有這些模型:Django的/的Postgres:選擇DISTINCT ON組
class Product(Model):
...
class Scanning(Model):
product = ForeignKey(..)
datetime = DateTimeField(...)
...
我試圖獲得了掃描是product.scanning.all()
組最新的一個產品每一個掃描。
s1 = (product1,01.01.1000)
s2 = (product2,01.01.1200)
s3 = (product1,01.01.1900)
s4 = (product2,01.01.1988)
s5 = (product3,01.01.2015)
s6 = (product3,01.01.1970)
將返回<s4,s3,s5>
Scanning.objects.filter(product__user=u,product__active=True).distinct('product_id').order_by('datetime')
引發例外:
ProgrammingError: SELECT DISTINCT ON expressions must match initial ORDER BY expressions LINE 1: SELECT DISTINCT ON ("productapp_scanning"."product_id") "pro... ^
如何使它工作?