Django ORM，将None datetime作为0插入MySQL

问题描述

我有一个MySQL数据库，除Django外，另一个应用程序正在使用该数据库.该应用程序使用'0000-00-00 00:00:00'作为日期时间的默认值.

I have a MySQL database that is used by another application besides Django. That application uses '0000-00-00 00:00:00' as default value for datetimes.

Django(v1.5.5)在读取数据库时将'0000-00-00 00:00:00'日期时间解释为None，而在写入数据库时​​将None解释为NULL.由于数据库将字段定义为NOT NULL，因此将导致错误.

Django (v1.5.5) interprets '0000-00-00 00:00:00' datetime as None when reading the database and None as NULL when writing into the database. This causes an error since the database defines the field as NOT NULL.

手动设置:

model.datetime = '0000-00-00 00:00:00'

不起作用，因为Django认为这是一个无效的日期.

Doesn't work because Django feels that this is an invalid date.

如何创建将None插入为'0000-00-00 00:00:00'的自定义日期时间字段?

How do I create a custom datetime field which inserts None as '0000-00-00 00:00:00'?

推荐答案

创建自定义DateTimeField并覆盖get_db_prep_value.该方法是从Django源复制粘贴的，并添加了一个用于处理None的案例.该值应该以数据库特定的方式进行转换，这样虽然有点怪异，但是只要数据库接受0000-00-00 00:00:00作为日期时间，它就可以工作.

Create a custom DateTimeField and override the get_db_prep_value. The method is copypasted from the django source and a case is added for handling None. The value should be converted in a database specific manner so this is a bit hacky but it works as long as the database accepts 0000-00-00 00:00:00 as a datetime.

from django.db import models

class ZeroDateTimeField(models.DateTimeField):
    def get_db_prep_value(self, value, connection, prepared=False):
        # Casts datetimes into the format expected by the backend
        if not prepared:
            value = self.get_prep_value(value)

        # Use zeroed datetime instead of NULL
        if value is None:
            return  "0000-00-00 00:00:00"

        else:
            return connection.ops.value_to_db_datetime(value)

此答案是为Django 1.5编写的，尚未测试对其他版本的支持.

This answer was written for Django 1.5 and support with other versions has not been tested.

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