[英]Django ORM query to retrieve objects from a table and most recent objects from another foreign-key-related table?
如何將下面的 SQL 查詢轉換為 Django ORM 語句,以便獲得相同的字段?
SELECT
entity_a.id AS entity_a__id,
entity_a.created_at AS entity_a__created_at,
MAX(entity_b.last_update) AS max__entity_b__last_update,
entity_b.id AS entity__b_id,
entity_b.datadump AS entity_b__datadump
FROM
entity_a
INNER JOIN
entity_b ON entity_a.id = entity_b.entity_a_id
WHERE
entity_a.created_at < '2020-03-10'
GROUP BY entity_a.id;
從django>=1.8
您可以使用annotate
和F
object 作為字段別名。 對於聚合,您可以使用ORM 的聚合特性
from django.db.models import F, Max
EntityA.objects.annotate(
entity_a__id=F('id'),
entity_a__created_at=F('created_at'),
entity__b_id=F('entity_b_id'),
entity_b__datadump=F('entity_b__datadump'),
max__entity_b__last_update=Max('entity_b__last_update')
).filter(
created_at__lt='2020-03-10',
).values(
'entity_a__id',
'entity_a__created_at',
'entity__b_id',
'entity_b__datadump',
'max__entity_b__last_update'
)
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