本文主要讲mysql中三种删除表的操作,delete语句、truncate语句以及drop语句的区别:简介:一.delete 1.删除整张表的数据:delete from table_name;2.删除部分数据,添加where子句:delete from table_name where...;3.说明 (1)属于DML语言,每次删除一行,都在事务日志中为所删除的每行记录一项。产生rollbac django mysql...
from django.db import connectioncursor = connection.cursor()cursor.execute("SELECT name FROM sqlite_master WHERE type='table';")tables = cursor.fetchall()for table in tables:cursor.execute(f"DELETE FROM {table[0]};") 然后输入exit函数退出该Django Shell环境。 exit() 可以了,现在可以重新创建迁...
using) def delete_model(self, request, obj): # Tell Django to delete objects from the 'other' database obj.delete(using=self.using) def get_queryset(self, request): # Tell Django to look for objects on the 'other' database. return super().get_queryset(request).using(self.using) ...
In total, this code does either one or zero database queries. The only deliberate optimization performed is using theemailsvariable. UsingQuerySet.exists()for theiforQuerySet.count()for the count would each cause additional queries. 使用QuerySet.update()和delete()¶ ...
4. 错误:DatabaseError: (1049, "Unknown database 'your_database_name'") 原因:指定的数据库不存在。 解决方法: 创建数据库: 创建数据库: 示例代码 以下是一个简单的 Django 项目配置示例: 代码语言:txt 复制 # settings.py import os BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(_...
self.conn.commit()deffetchall(self):returnself.cursor.fetchall()deffetchone(self):returnself.cursor.fetchone()def__del__(self): self.close()classMysql_pool:def__init__(self, host, user, password, database): self.host = host
ForeignKey(BookInfo, on_delete=models.CASCADE, verbose_name=u'图书') def __str__(self): return self.name class Meta: db_table = 'HeroInfo' verbose_name = u'人物信息' verbose_name_plural = verbose_name ordering = ['id'] 设计模型的时候出现了几个之前没用过的字段类型,在这里简单介绍一...
调用一个模型类对象的delete方法的时候就可以实现对模型类对应数据表数据的删除。 二、自关联 自关联是一种特殊的一对多的关系。 【案例】:显示广州市的上级地区和下级地区。 地区表:id, atitle, aParent_id; mysql终端中批量执行sql语句:source areas.sql; ...
How to Back Up and Restore a MySQL Database {Easy Tutorial} (phoenixnap.com) 清理migrations表 清理migrations实操 PS D:\repos\ELA\backEnd\ela> .\manage.py migrate --fake word zero Operations to perform: Unapply all migrations: word ...
Expand All/Collapse All Object-relational mapper Define your data models entirely in Python. You get a rich, dynamic database-access API for free — but you can still write SQL if needed. Read more fromdjango.dbimportmodelsclassBand(models.Model):"""A model of a rock band."""name=mo...