django 數據修改

-----------------------------------------改（update和save） ----------------------------------------

#---------------- update方法直接設定對應屬性----------------（推薦）
    models.Book.objects.filter(id=3).update(title="PHP")
    ##sql:
    ##UPDATE "app01_book" SET "title" = 'PHP' WHERE "app01_book"."id" = 3; args=('PHP', 3)


#--------------- save方法會將所有屬性重新設定一遍,效率低-----------
    obj=models.Book.objects.filter(id=3)[0]
    obj.title="Python"
    obj.save()
# SELECT "app01_book"."id", "app01_book"."title", "app01_book"."price", 
# "app01_book"."color", "app01_book"."page_num", 
# "app01_book"."publisher_id" FROM "app01_book" WHERE "app01_book"."id" = 3 LIMIT 1; 
# 
# UPDATE "app01_book" SET "title" = 'Python', "price" = 3333, "color" = 'red', "page_num" = 556,
# "publisher_id" = 1 WHERE "app01_book"."id" = 3; 

 

修改某列值方法；F查詢

 from django.db.models import F #導入使用F查詢 

def wuerqi(req):
    # f查詢修改數據
    # 想同時給所有書籍價格加10的操作時就需要f查詢來修改價格
    Book.objects.all().update(price=F('price')+10)

    return HttpResponse('修改成功')

 

 from django.db.models import Q 

    #1 Q對象(django.db.models.Q)可以對關鍵字參數進行封裝，從而更好地應用多個查詢
    q1=models.Book.objects.filter(Q(title__startswith='P')).all()
    print(q1)#[<Book: Python>, <Book: Perl>]

    # 2、可以組合使用&,|操作符，當一個操作符是用於兩個Q的對象,它產生一個新的Q對象。  或
    Q(title__startswith='P') | Q(title__startswith='J')

    # 3、Q對象可以用~操作符放在前面表示否定，也可允許否定與不否定形式的組合     非　　
    Q(title__startswith='P') | ~Q(pub_date__year=2005)

    # 4、應用范圍：

    # Each lookup function that takes keyword-arguments (e.g. filter(),
    #  exclude(), get()) can also be passed one or more Q objects as
    # positional (not-named) arguments. If you provide multiple Q object
    # arguments to a lookup function, the arguments will be “AND”ed
    # together. For example:

    Book.objects.get(
        Q(title__startswith='P'),
        Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6))
    )

    #sql:
    # SELECT * from polls WHERE question LIKE 'P%'
    #     AND (pub_date = '2005-05-02' OR pub_date = '2005-05-06')

    # import datetime
    # e=datetime.date(2005,5,6)  #2005-05-06

    # 5、Q對象可以與關鍵字參數查詢一起使用，不過一定要把Q對象放在關鍵字參數查詢的前面。
    # 正確：
    Book.objects.get(
        Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6)),
        title__startswith='P')
    # 錯誤：
    Book.objects.get(
        question__startswith='P',
        Q(pub_date=date(2005, 5, 2)) | Q(pub_date=date(2005, 5, 6)))