MySQL database_MySQL and Python interaction_Python operation MySQL steps and additions, deletions and changes

MySQL database

MySQL and Python interaction

Python operation MySQL steps

Import module

• Introduce the pymysql module in the py file

from pymysql import *

Connection object

• Used to establish a connection with the database
• Create an object: call the connect() method

conn=connect(参数列表)

• Parameter host: the connected mysql host, if the local machine is'localhost'
• Parameter port: the port of the connected mysql host, the default is 3306
• Parameter database: the name of the database
• Parameter user: the user name of the connection
• Parameter password: the password of the connection
• Parameter charset: the encoding method used for communication, utf8 is recommended

Object method

• close()Close the connection
• commit() submit
• cursor() returns a Cursor object, which is used to execute SQL statements and obtain results

Cursor object

• Used to execute SQL statements, the most frequently used statements are select, insert, update, delete
• Obtain the Cursor object: call the cursor() method of the Connection object

cs1=conn.cursor()

Object method

• close()close
• execute(operation [, parameters]) executes the statement, returns the number of rows affected, mainly used to execute insert, update, delete statements, and can also execute create, alter, drop and other statements
• When fetchone() executes the query statement, it obtains the first row data of the query result set and returns a tuple
• When fetchall() executes the query, get all the rows of the result set, one row forms a tuple, and then assemble these elements into a tuple and return

Object properties

• rowcount is a read-only attribute, indicating the number of rows affected after the most recent execute() execution
• connection gets the current connection object

Python operates MySQL to perform'addition, deletion, modification, and check'

Additions and deletions

from pymysql import *

def main():
    # 创建Connection连接
    conn = connect(host='localhost',port=3306,database='jing_dong',user='root',password='此处填写密码',charset='utf8')
    # 获得Cursor对象
    cs1 = conn.cursor()
    # 执行insert语句，并返回受影响的行数：添加一条数据
    # 增加
    count = cs1.execute('insert into goods_cates(name) values("硬盘")')
    #打印受影响的行数
    print(count)

    count = cs1.execute('insert into goods_cates(name) values("光盘")')
    print(count)

    # # 更新
    # count = cs1.execute('update goods_cates set name="机械硬盘" where name="硬盘"')
    # # 删除
    # count = cs1.execute('delete from goods_cates where id=6')

    # 提交之前的操作，如果之前已经之执行过多次的execute，那么就都进行提交
    conn.commit()

    # 关闭Cursor对象
    cs1.close()
    # 关闭Connection对象
    conn.close()

if __name__ == '__main__':
    main()

Query a row of data

from pymysql import *

def main():
    # 创建Connection连接
    conn = connect(host='localhost',port=3306,user='root',password='此处填写码',database='jing_dong',charset='utf8')
    # 获得Cursor对象
    cs1 = conn.cursor()
    # 执行select语句，并返回受影响的行数：查询一条数据
    count = cs1.execute('select id,name from goods where id>=4')
    # 打印受影响的行数
    print("查询到%d条数据:" % count)

    for i in range(count):
        # 获取查询的结果
        result = cs1.fetchone()
        # 打印查询的结果
        print(result)
        # 获取查询的结果

    # 关闭Cursor对象
    cs1.close()
    conn.close()

if __name__ == '__main__':
    main()

Query multiple rows of data

from pymysql import *

def main():
    # 创建Connection连接
    conn = connect(host='localhost',port=3306,user='root',password='mysql',database='jing_dong',charset='utf8')
    # 获得Cursor对象
    cs1 = conn.cursor()
    # 执行select语句，并返回受影响的行数：查询一条数据
    count = cs1.execute('select id,name from goods where id>=4')
    # 打印受影响的行数
    print("查询到%d条数据:" % count)

    # for i in range(count):
    #     # 获取查询的结果
    #     result = cs1.fetchone()
    #     # 打印查询的结果
    #     print(result)
    #     # 获取查询的结果

    result = cs1.fetchall()
    print(result)

    # 关闭Cursor对象
    cs1.close()
    conn.close()

if __name__ == '__main__':
    main()