Python接入MySQL实现增删改查

Python接入MySQL实现增删改查

1. 打开数据库连接，创建数据库和表
   基本语法如下：

   execute(query, args=None)
   # query为字符串类型的sql语句
   # args：可选的序列或映射，用于query的参数值。
   # 如果args为序列，query中必须使用%s做占位符；
   # 如果args为映射，query中必须使用%(key)s做占位符
   

   案例：数据库名learning，表名houses，字段name house_location purchasing_year

   import pymysql
   db = pymysql.connect('localhost', 'root', "password")       # 打开数据库连接，password替换为本机数据库密码
   cursor = db.cursor()
   cursor.execute('drop database learning;')
   cursor.execute('create database learning;')
   cursor.execute('use learning')
   sql_create = """create table houses (name VARCHAR(100) NOT NULL, house_location VARCHAR(100) NOT NULL, purchasing_year VARCHAR(100) NOT NULL);"""
   cursor.execute(sql_create)
   

2. 插入

   # 插入
   sql_insert = """insert into houses values(%s,%s,%s);"""
   cursor.execute(sql_insert,('梦璃','南天门',1995))       # 插入单条数据
   cursor.executemany(sql_insert,[('紫英','蜀山',1996),('天河','石沉',1997),('菱纱','溪洞',1998)])       # 插入多条数据
   

3. 查询

   sql_select = """select * from houses"""
   # 单条查询
   cursor.execute(sql_select)
   while 1:
       result = cursor.fetchone()
       if result is None:
           # 取完所有结果
           break
       print(result)
   
   # 多条查询，取3条数据
   cursor.execute(sql_select)
   Result = cursor.fetchmany(3)
   for res in Result:
       print(res)
   
   # 多条查询，取所有数据
   cursor.execute(sql_select)
   Result = cursor.fetchall()
   for res in Result:
       print(res)
   

4. 更新

   # 更新一条数据
   sql_update = """update houses set purchasing_year=2000 where name='菱纱';"""
   cursor.execute(sql_update)
   cursor.execute(sql_select)
   Result = cursor.fetchall()
   for res in Result:
       print(res)
   # 更新多条数据
   sql_update = """update houses set purchasing_year=%s where name=%s;"""
   cursor.executemany(sql_update,[(2018,'梦璃'),(2019,'紫英')])
   cursor.execute(sql_select)
   Result = cursor.fetchall()
   for res in Result:
       print(res)
   # 回滚事务
   db.rollback()
   cursor.execute(sql_select)
   Result = cursor.fetchall()
   for res in Result:
       print(res)
   

5. 删除

   # 删除1条数据
   sql_delete = """delete from houses where name='梦璃';"""
   cursor.execute(sql_delete)
   cursor.execute(sql_select)
   Result = cursor.fetchall()
   for res in Result:
       print(res)
   # 删除多条数据
   sql_delete = """delete from houses where name=%s;"""
   cursor.executemany(sql_delete,[('天河'),('紫英')])
   cursor.execute(sql_select)
   Result = cursor.fetchall()
   for res in Result:
       print(res)
   

6. 关闭游标，关闭数据库连接

   cursor.close()                                           # 关闭游标
   db.commit()
   db.close()                                               # 关闭数据库连接
   print('sql执行成功')