Python操作MySQL基础使用

Python操作MySQL基础使用

链接数据库并查询数据

import pymysql

# 链接数据库
conn = pymysql.connect(
    host='10.5.6.250',
    port=3306,
    user='root',
    password='********'
)

# 查看MySQL版本信息
print(conn.get_server_info())  # 5.5.27

# 获取到游标对象
cursor = conn.cursor()

# 选择数据库
conn.select_db("hanligang_data")

# 使用游标对象执行sql语句
sql = "select * from tstudent"
cursor.execute(sql)

# 获取查询结果
results: tuple = cursor.fetchall()
print(results)  # 结果是一个大元组，里面包含了每一行数据的小元组

for r in results:
    print(r)

conn.close()  # 关闭

查询结果（里面身份证为for循环生产的虚拟数据）：

('0000000118', '魏欣若', '男', '6968390833530048', '1984-09-19 00:00:00.000', '[email protected]', '开发', '2019-12-18 17:58:52.85')
('0000000119', '胡辉香', '男', '1687819817472568', '1985-02-18 00:00:00.000', '[email protected]', '开发', '2019-12-18 17:58:52.85')
('0000000120', '姜利维', '男', '1367699597056572', '1988-10-17 00:00:00.000', '[email protected]', '网络', '2019-12-18 17:58:52.85')
('0000000121', '马文霞', '男', '2921194355462422', '1984-03-11 00:00:00.000', '[email protected]', '测试', '2019-12-18 17:58:52.85')
('0000000122', '于爽轮', '女', '3826182221042389', '1981-03-27 00:00:00.000', '[email protected]', '网络', '2019-12-18 17:58:52.85')
('0000000123', '吴军雪', '女', '361896711952425', '1988-10-05 00:00:00.000', '[email protected]', '开发', '2019-12-18 17:58:52.85')
('0000000124', '廖菲以', '男', '6206075708967862', '1984-10-07 00:00:00.000', '[email protected]', '开发', '2019-12-18 17:58:52.85')
('0000000125', '孔国馨', '男', '6196758315299228', '1984-04-07 00:00:00.000', '[email protected]', '开发', '2019-12-18 17:58:52.85')
('0000000126', '李伟伟', '女', '9973233711794250', '1988-08-05 00:00:00.000', '[email protected]', '开发', '2019-12-18 17:58:52.85')

修改库或者表

import pymysql

db = pymysql.connect(
host='localhost', user='root', password='mysql',  #连接到数据库需要指定的最少信息
                     db = 'demo', database='demo', #指定选择的数据库，任选一个都可，前面是简写
                     passwd='mysql', #密码也可以用passwd简写形式
                     autocommit=True, #设置修改自动提交到数据库
                     auth_plugin_map='mysql_native_password'
                     ) #设置身份认证，8.0版本之后建议加上
cursor = db.cursor() #创建一个指针，之后基本所有的操作都是使用指针来实现
cursor.execute('show databases;') #执行SQL语句
db.commit() #将修改提交到数据库——如果连接时参数autocommit设置为false要加上
cursor.fetchall() #获取上一条SQL语句的执行结果，如查询结果等
cursor.fetchone() #获取执行结果的一行
db.close() #关闭数据库

常用方法

为了让程序更加健壮，我们一般不会链接数据库这样调用该函数，先不说麻烦与否，如果我们经常要修改连接参数，那么我们所有调用地方都会修改，这样的代码十分不健壮。所以我们应该使用模块化进行解决，代码如下：

import pymysql
 
def connect_mysql():
    db_config = {
        'host':'127.0.0.1',
        'port':3306,
        'user':'ian',
        'password':'ian123',
        'charset':'utf8'
    }
    conn = pymysql.connect(**db_config)
    return conn

查询函数

def query_students_fetchone():
    sql = 'SELECT * FROM students'
    rows = cursor.execute(sql)
    print('There are %d students' % rows)
 
    for i in range(rows):
        student = cursor.fetchone()
        print(student)

增删数据库
增删改，操作方式都一样，只是mysql语句的不同，返回的值是影响的行数。需要注意的是，我们需要提交事务，如果不提交事务，语句是不执行的，只是显示执行成功，但是表中并没有进行相关操作。代码如下：

import pymysql
 
def insert_mysql():
    no = int(input('编号: '))
    name = input('名称: ')
    location = input('所在地: ')
 
    # 1. 创建连接
    conn = pymysql.connect(host='127.0.0.1', port=3306,
                       user='ian', password='ian123',
                       database='test', charset='utf8')
    try:
        # 2. 获取游标对象
        with conn.cursor() as cursor:
            # 3. 通过游标对象向数据库服务器发出SQL语句
            affected_rows = cursor.execute(
                'insert into `tb_test` values (%s, %s, %s)',
                (no, name, location)
            )
            if affected_rows == 1:
                print('新增成功!!!')
        # 4. 提交事务
        conn.commit()
    except pymysql.MySQLError as err:
        # 4. 回滚事务
        conn.rollback()
        print(type(err), err)
    finally:
        # 5. 关闭连接释放资源
        conn.close()
 
def del_mysql():
    no = int(input('编号: '))
 
    # 1. 创建连接
    conn = pymysql.connect(host='127.0.0.1', port=3306,
                       user='ian', password='ian123',
                       database='test', charset='utf8',
                       autocommit=True)
    try:
        # 2. 获取游标对象
        with conn.cursor() as cursor:
            # 3. 通过游标对象向数据库服务器发出SQL语句
            affected_rows = cursor.execute(
                'delete from `tb_dept` where `dno`=%s',
                (no, )
        )
            if affected_rows == 1:
                print('删除成功!!!')
    finally:
        # 5. 关闭连接释放资源
        conn.close()
 
insert_mysql()
del_mysql()
 

封装mysql类

import pymysql
from pathlib import Path
 
class ConnectMsql:
    def __init__(self, host='127.0.0.1', port=3306, user='ian',
                 password='ian123', database="test", filename: str = "test.sql"):
        """
        :param host:        域名
        :param port:        端口
        :param user:        用户名
        :param password:    密码
        :param database:    数据库名
        :param filename:    文件名称
        """
 
        self._host: str = host
        self._port: int = port
        self._user: str = user
        self._password: str = password
        self._database: str = database
        self._file_path = Path(__file__).parent.joinpath(filename)
 
    def _show_databases_and_create(self):
        """
        查询数据库是否存在，不存在则进行新建操作
        :return:
        """
        connection = pymysql.connect(host=self._host, port=self._port, user=self._user, password=self._password,
                                     cursorclass=pymysql.cursors.DictCursor)
        with connection:
            with connection.cursor() as cursor:
                cursor.execute('show databases;')
                result = cursor.fetchall()
                results = self._database not in tuple(x["Database"] for x in result)
 
        if results:
            with connection.cursor() as cursor:
                cursor.execute(f'create database {self._database};')
            with connection.cursor() as cursor:
                cursor.execute('show databases;')
                result = cursor.fetchall()
                results = self._database in tuple(x["Database"] for x in result)
            return results if results else result
        else:
            return True
 
    def _export_databases_data(self):
        """
        读取.sql文件，解析处理后，执行sql语句
        :return:
        """
        if self._show_databases_and_create() is True:
            connection = pymysql.connect(host=self._host, port=self._port, user=self._user, password=self._password,
                                         database=self._database, charset='utf8')
            # 读取sql文件，并提取出sql语句
            results, results_list = "", []
            with open(self._file_path, mode="r+", encoding="utf-8") as r:
                for sql in r.readlines():
                    # 去除数据中的“\n”和“\r”字符
                    sql = sql.replace("\n", "").replace("\r", "")
                    # 获取不是“--”开头且不是“--”结束的数据
                    if not sql.startswith("--") and not sql.endswith("--"):
                        # 获取不是“--”的数据
                        if not sql.startswith("--"):
                            results = results + sql
 
                # 根据“;”分割数据，处理后插入列表中
                for i in results.split(";"):
                    if i.startswith("/*"):
                        results_list.append(i.split("*/")[1] + ";")
                    else:
                        results_list.append(i + ";")
 
            # 执行sql语句
            with connection:
                with connection.cursor() as cursor:
                    # 循环获取sql语句
                    for x in results_list[:-1]:
                        # 执行sql语句
                        cursor.execute(x)
                        # 提交事务
                        connection.commit()
                    else:
                        return "sql全部语句执行成功 ！"
 
    @property
    def sql_run(self):
        """
        执行方法
        :return:
        """
        return self._export_databases_data()
 
if __name__ == '__main__':
    res = ConnectMsql().sql_run
    print(res)