on_delete = None:删除关联表的数据时,当前表与关联表的filed的行为。 on_delete = models.DO_NOTHING:你删你的,父亲(外键)不想管你 on_delete = models.PROTECT:保护模式,如采用这个方法,在删除关联数据时会抛出ProtectError错误 on_delete = models.SET_DEFAULT:设置默认值,删除子表字段时,外键字段设置为默...
#on_delete=models.PROTECT, #关联保护,因为邮箱数据被用户表关联,所以该邮箱不允许被删除,并且触发ProtectError #Cannot delete some instances of model'EmailInfo'because they are referenced through aprotectedforeign key:'UserInfo.el'", <QuerySet [<UserInfo: UserInfo object>]> #on_delete=models.SET_NUL...
on_delete=models.CASCADE) on_delete参数如下: CASCADE：级联操作。
批量更新数据时,先是进行数据过滤,然后再调用delete方法进行一次性地删除。下面的语句将生成类似delete from...where...的SQL语句。 Product.objects.filter(name__contains='name query').delete() 如果是通过运行普通Python脚本的方式而不是在view中调用上述的代码的,别忘了先在脚本中进行django的初始化: importos...
ForeignKey.on_delete emulated only 汇报人:mischiew@…属主:nobody 组件:Database layer (models, ORM)版本:1.3 严重性:Normal关键词:foreignkey,ondelete 抄送:Triage Stage:Unreviewed Has patch:否Needs documentation:否 Needs tests:否Patch needs improvement:否...
The name of the foreign key on the model. In most cases this will be dealt with automatically, but fk_name must be specified explicitly if there are more than one foreign key to the same parent model. InlineModelAdmin.formset¶ This defaults to BaseInlineFormSet. Using your own formset...
There are a few restrictions on the intermediate model: Your intermediate model must contain one - and only one - foreign key to the source model (this would be Group in our example), or you must explicitly specify the foreign keys Django should use for the relationship using ManyToManyField....
Gender = models.ForeignKey('Coding',on_delete=models.CASCADE) # 关联Coding表格 ForeignKey (othermodel,on_delete,**options) 有两个必选的参数 : 第一个参数:关联的表格(主表),在默认的情况下,外键储存的是主表的主键(Primary key)。上面的例子里,关联到 Coding 表格,默认情况下储存 Coding 表格的主键 ...
字表中外键字段的数据类型要与父表中的数据类型一致...建立外键语法:[constraint 外键名] foreign key (子表字段名 ) references 父表 (父表字段名) [on delete {restrict...alter table 表名 drop foreign key 外键名; 注意:删除外键后发现 desc 查看索引标志还在,其实外键也是一种索引,需要将外键索引删除...
Django how to conditionally update a field value based on other field related by foreign key? Posted on 2022年7月30日 at 19:16 byStack OverflowRSS I have a Test model which has several skillareas in it (each test can have sevral skillarea: one to many) and each skillarea has several...