疯狂的Django 之深度外键跨表查找之疯狂INNER JOIN

定义Model:

from django.db import models

class Moreinfo(models.Model):

    weight = models.FloatField()
    height = models.FloatField()

class Detail(models.Model):

    sex = models.CharField(max_length=20)
    age = models.IntegerField()
    moreinfo = models.ForeignKey(Moreinfo)

class Usr(models.Model):

    name = models.CharField(max_length=20)
    money = models.FloatField()
    detail = models.ForeignKey(Detail)

class Product(models.Model):

    name = models.CharField(max_length=20)
    price = models.FloatField()

class Record(models.Model):

    buyer = models.ForeignKey(Usr, related_name='+',)
    seller = models.ForeignKey(Usr, related_name='+',)
    product = models.ForeignKey(Product)
    conut = models.IntegerField()

查询语句:

>>> x=Record.objects.filter(Q(seller__detail__age__gt=20)|Q(buyer__detail__age__gt=20))
>>> print(x.query)
SELECT "tt_record"."id", "tt_record"."buyer_id", "tt_record"."seller_id", "tt_record"."product_id", "tt_record"."conut" FROM "tt_record" INNER JOIN "tt_usr" ON ("tt_record"."seller_id" = "tt_usr"."id") INNER JOIN "tt_detail" ON ("tt_usr"."detail_id" = "tt_detail"."id") INNER JOIN "tt_usr" T4 ON ("tt_record"."buyer_id" = T4."id") INNER JOIN "tt_detail" T5 ON (T4."detail_id" = T5."id") WHERE ("tt_detail"."age" > 20 OR T5."age" > 20)

整理如下:

SELECT "tt_record"."id", "tt_record"."buyer_id", "tt_record"."seller_id", "tt_record"."product_id", "tt_record"."conut"
FROM "tt_record"
INNER JOIN "tt_usr" ON ("tt_record"."seller_id" = "tt_usr"."id")
INNER JOIN "tt_detail" ON ("tt_usr"."detail_id" = "tt_detail"."id")
INNER JOIN "tt_usr" T4 ON ("tt_record"."buyer_id" = T4."id")
INNER JOIN "tt_detail" T5 ON (T4."detail_id" = T5."id")
WHERE ("tt_detail"."age" > 20 OR T5."age" > 20)