批量插入数据
单条插入autocommit的，每插入一次commit一次；批量是插入完成后一次性commit的，效率相对较高。
>>> Entry.objects.bulk_create([
... Entry(headline="Django 1.0 Released"),
... Entry(headline="Django 1.1 Announced"),
... Entry(headline="Breaking: Django is awesome")
... ])
批量更新
Product.objects.filter(name__contains='name').update(name='new name')
批量删除
EnrollSupplemental.objects.filter(account=account).delete()