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我想爲我的一個項目構建一個複雜的(對我來說)查詢。 Django版本是1.11.4,PostgreSQL版本是9.6。Django 1.11.4 Postgresql SELECT ARRAY到django orm
這裏是模型。
class Event(models.Model):
...
name = models.CharField(max_length=256)
classification = models.ForeignKey("events.Classification", related_name="events", null=True, blank=True)
...
class Classification(models.Model):
...
segment = models.ForeignKey("events.ClassificationSegment", related_name="classifications", blank=True, null=True)
...
class ClassificationSegment(models.Model):
...
name = models.CharField(max_length=256)
...
我封鎖了某處,無法繼續。
from django.db.models import CharField, Value as V
from django.db.models.functions import Concat
from django.contrib.postgres.aggregates import ArrayAgg
from django.db.models import OuterRef, Subquery
import events.models
event_subquery = events.models.Event.objects.filter(classification__segment=OuterRef('pk')) \
.annotate(event=Concat(V('{id:'), 'id', V(', name:"'), 'name', V('"}'), output_field=CharField()))
final_list = events.models.ClassificationSegment.objects.annotate(
event_list=ArrayAgg(Subquery(event_subquery.values('event')[:6])))
我有一個原始查詢。這裏是。
final_events = events.models.ClassificationSegment.objects.raw('SELECT "events_classificationsegment"."id", "events_classificationsegment"."name", (SELECT ARRAY(SELECT CONCAT(\'{id:\', CONCAT(U0."id", CONCAT(\',\', \'name:"\', U0."name", \'"}\'))) AS "event" FROM "events_event" U0 INNER JOIN "events_classification" U1 ON (U0."classification_id" = U1."id") WHERE U1."segment_id" = ("events_classificationsegment"."id") LIMIT 6)) AS "event_list" FROM "events_classificationsegment"')
您可以在截圖中看到結果。我想我是對的。誰能幫我?
感謝。