前言前面在admin后臺頁面通過設(shè)置外鍵，可以選擇下拉框的選項,，本篇主要講解關(guān)于外鍵（ForeignKey）的查詢 models設(shè)計在上一篇的基礎(chǔ)上新增一個BankName表,，Card表通過外鍵關(guān)聯(lián)到BankName class BankName(models.Model):
'''銀行信息'''
bank_name = models.CharField(max_length=50, verbose_name="銀行名稱", default="")
city = models.CharField(max_length=30, verbose_name="城市", default="")
point = models.CharField(max_length=60, verbose_name="網(wǎng)點", default="")
class Meta:
verbose_name = '銀行'
verbose_name_plural = verbose_name
def __str__(self):
return self.bank_name
class Card(models.Model):
'''銀行卡 基本信息'''
card_id = models.CharField(max_length=30, verbose_name="卡號", default="")
card_user = models.CharField(max_length=10, verbose_name="姓名", default="")
add_time = models.DateField(auto_now=True, verbose_name="添加時間")
bank_info = models.ForeignKey(BankName, on_delete=models.CASCADE, default="")
class Meta:
verbose_name = "銀行卡賬戶_基本信息"
verbose_name_plural = '銀行卡賬戶'
def __str__(self):
return self.card_id
class CardDetail(models.Model):
'''銀行卡詳情信息'''
card = models.OneToOneField(Card,
on_delete=models.CASCADE,
verbose_name="卡號"
)
tel = models.CharField(max_length=30, verbose_name="電話", default="")
mail = models.CharField(max_length=30, verbose_name="郵箱", default="")
city = models.CharField(max_length=10, verbose_name="城市", default="")
address = models.CharField(max_length=30, verbose_name="詳細(xì)地址", default="")
class Meta:
verbose_name = "賬戶_個人資料"
verbose_name_plural = verbose_name
def __str__(self):
return self.card.card_user之后執(zhí)行 makemigrations 和migrate,，同步數(shù)據(jù) python manage.py makemigrations
python manage.py migrate
shell模式新增測試為了調(diào)試方便,，可以使用django的shell模式,，對表的數(shù)據(jù)增刪改查操作,，打開cmd,，cd到manage.py目錄 python manage.py shell
先新增數(shù)據(jù)測試數(shù)據(jù) D:\web_djo\helloworld>python manage.py shell
>>> from hello.models import Card, BankName
>>> a = BankName.objects.create(bank_name='上海銀行', city='上海', point='徐家匯區(qū)')
>>> c = Card.objects.create(card_id='62270121022100000', card_user='張三', bank_info=a)
正向查詢根據(jù)Card表的card_id，去查詢關(guān)聯(lián)的對應(yīng)的BankName相關(guān)信息,，這個相對來說簡單一點 >>> from hello.models import BankName, Card
>>> cardxx=Card.objects.get(card_id='62270121022100000')
>>> cardxx.card_user
'張三'
>>> cardxx.bank_info
<BankName: 上海銀行>
>>> cardxx.bank_info.bank_name
'上海銀行'
>>> cardxx.bank_info.city
'上海'
>>>反向查詢_set如果想通過銀行名稱“上海銀行”,，查詢到此銀行關(guān)聯(lián)多少張卡，并且查詢其中一個銀行卡的信息,。
反向查詢,，當(dāng)ForeignKey沒設(shè)置related_name參數(shù)，默認(rèn)是通過關(guān)聯(lián)表的名稱加_set去查詢 >>> bank = BankName.objects.get(bank_name='上海銀行')
>>> bank.city
'上海'
# 反向查詢,，表名稱_set
>>> bank.card_set.all()
<QuerySet [<Card: 62270121022100000>]>
# count()函數(shù)統(tǒng)計
>>> bank.card_set.all().count()
1
>>> bank.card_set.all()[0].card_id
'62270121022100000'
>>>related_name當(dāng)Card表的外鍵（ForeignKey）只有一個時，可以通過_set去查詢到,，當(dāng)有多個外鍵時,，就無法查詢具體哪個外鍵了，這時候就需要加個related_name參數(shù)。 class CardGrade(models.Model):
'''會員等級'''
nub = models.CharField(max_length=50, verbose_name="會員等級", default="")
class Meta:
verbose_name = '會員等級'
verbose_name_plural = verbose_name
class BankName(models.Model):
'''銀行信息'''
bank_name = models.CharField(max_length=50, verbose_name="銀行名稱", default="")
city = models.CharField(max_length=30, verbose_name="城市", default="")
point = models.CharField(max_length=60, verbose_name="網(wǎng)點", default="")
class Meta:
verbose_name = '銀行'
verbose_name_plural = verbose_name
def __str__(self):
return self.bank_name
class Card(models.Model):
'''銀行卡 基本信息'''
card_id = models.CharField(max_length=30, verbose_name="卡號", default="")
card_user = models.CharField(max_length=10, verbose_name="姓名", default="")
add_time = models.DateField(auto_now=True, verbose_name="添加時間")
bank_info = models.ForeignKey(BankName, related_name='card_bank', on_delete=models.CASCADE, default="")
grade = models.ForeignKey(CardGrade, related_name='card_grade', on_delete=models.CASCADE, default="")
class Meta:
verbose_name = "銀行卡賬戶_基本信息"
verbose_name_plural = '銀行卡賬戶'
def __str__(self):
return self.card_idrelated_name參數(shù)相當(dāng)于給這個外鍵取了個別名,，方便多個外鍵時候去識別,。以下是新增數(shù)據(jù)和正向查詢 # 新增數(shù)據(jù)
>>> from hello.models import CardGrade,BankName,Card
>>> n=CardGrade.objects.create(nub='黃金會員')
>>> b=BankName.objects.create(bank_name='北京銀行',city='北京')
>>> c=Card.objects.create(card_id='666555000111',card_user='楊過', bank_info=b,
grade=n)
# 正向查詢
>>> c.grade.nub
'黃金會員'
>>> c.bank_info.city
'北京'
>>>反向查詢需要用到related_name參數(shù)，如下 # CardGrade表查Card表
>>> nnn=CardGrade.objects.get(nub='黃金會員')
>>> nnn.card_grade.all()
<QuerySet [<Card: 666555000111>]>
>>> nnn.card_grade.all()[0].card_id
'666555000111'
# BankName表查Card表
>>> bbb=BankName.objects.get(bank_name='上海銀行')
>>> bbb.card_bank.all()
<QuerySet [<Card: 62270121022100000>]>
>>> bbb.card_bank.all()[0].card_id
'62270121022100000'
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