ORM正向和反向查詢

表結構

from django.db import models

# create your models here.
class publisher(models.model):
id = models.autofield(primary_key=true)
name = models.charfield(max_length=32)
class book(models.model):
id = models.autofield(primary_key=true)
name = models.charfield(max_length=32)
publisher = models.foreignkey('publisher', related_name='person_book', related_query_name='ooxx')

# book表

id title pubtime person_id
書1 1533225600000 1
書2 1533225600000 1
書3 1534435200000 1
書4 1535644800000 2
書5 1535126400000 3

# publisher表

id name 
1 出版社1 
2 出版社2 
3 出版社3

反向查詢：普通表去查外來鍵所在的表，publisher >> book

正向查詢，基於物件跨表查詢

book_obj = models.book.objects.all()  # 取到書籍物件

book_obj.publisher.name # 書籍的出版社名字，html
book_obj.person.id # 書籍的出版社id，html

models.book.objects.filter(id=1).values('publisher__name')  # 查詢id是1的書的出版社的名字，一條雙下劃線就是跨一張表

models.book.objects.filter(id=1).values_list('publisher__name')

物件查詢 obj.表名_set()

publisher_obj = models.publisher.objects.first()  # 找到第乙個出版社物件

ret = publisher_obj.book_set.all() # 找到第乙個出版社出版的所有數
for i in ret: # 迴圈物件
print(i.name) # 列印出每乙個書的書名

publisher_obj = models.publisher.objects.first()  # 找到第乙個出版社物件

books = publisher_obj.book_set.all() # 找到第乙個出版社出版的所有書
titles = books.values_list("name") # 找到第乙個出版社出版的所有書的書名
print(titles)
因為使用了releted_name,就是用person_book代替了表字段名字
表字段person = models.foreignkey(person, related_name='person_book')
所以這一這樣寫
books = publisher_obj.person_book.all()
titles = books.values_list('name')
print(titles)
如果表字段person = models.foreignkey(person, related_name='person_book'，related_query_name="xxoo")
related_query_name="xxoo"，這裡表示跨表查詢xxoo代替表的名字book
books = publisher_obj.ooxx_set.all()

ret = models.publisher.objects.filter(id=1).values_list('person_book__name')

person_book是通過releted_name給對應關係起的名字，通過person_book就找到了關聯的表，再通過雙下劃線找到name
print(ret)

import os

if __name__ == '__main__':
# 載入django專案的配置資訊
os.environ.setdefault("django_settings_module", "專案名.settings")
# 匯入django，並啟動django專案
import django
django.setup()
# 查詢id為1的出版社出版的所有書的name
ret = models.publisher.objects.filter(id=1).values_list('person_book__name')
print(ret)

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