python连接数据库,相关数据处理

随机生成一千个数据插入large_db中

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import pandas as pd
from sqlalchemy import create_engine
from faker import Faker

# 初始化faker对象
faker = Faker()
data = []

# 生成虚拟数据
for _ in range(1000):
    data.append([faker.name(), faker.address(), faker.email()])

df = pd.DataFrame(data, columns=['name', 'address', 'email'])

# 创建数据库引擎
engine = create_engine("mysql+pymysql://root:123456@localhost/large_db")

# 将DataFrame写入MySQL数据库中的'users'表
df.to_sql('users', con=engine, if_exists='append', index=False, chunksize=100)
# 访问 https://www.jetbrains.com/help/pycharm/ 获取 PyCharm 帮助

优化查询

分页查询：

USE large_db;
SET @start_time=Now0;
SELECT SOL_NO_CACHE *FROM users  Limit 100 OFFSET 1000;
SET @end_time=Nowd;
SELECT TIMEDIFF(@end_time,@start_time)AS query_duration;

索引查询：

CREATE INDEX idx_ name ON user(name);
CREATE INDEX idx_email ON users(email);
SET @start_time=Now();
SEIELCT SOL_NO_CACHE*FROM users WHERE name=“John Doe”;
SET @end_time=Now();
SELECT TIMEDIFF(@end_time,@start_time）AS query_duration;

在pycharm中版本查询：

import pymysql

# 连接MySQL数据库
connection = pymysql.connect(
    host='localhost',
    user='your_username',    # 替换为你的MySQL用户名
    password='your_password',  # 替换为你的MySQL密码
    db='your_database',      # 替换为你的数据库名称
    charset='utf8mb4',
    cursorclass=pymysql.cursors.DictCursor
)

try:
    with connection.cursor() as cursor:
        # 执行SQL查询
        sql = "SELECT VERSION()"
        cursor.execute(sql)
        result = cursor.fetchone()
        print("Database version:", result['VERSION()'])

finally:
    connection.close()

单字段查询：

import pymysql

# 连接MySQL数据库
connection = pymysql.connect(
    host='localhost',
    user='your_username',    # 替换为你的MySQL用户名
    password='your_password',  # 替换为你的MySQL密码
    db='your_database',      # 替换为你的数据库名称
    charset='utf8mb4',
    cursorclass=pymysql.cursors.DictCursor
)

try:
    with connection.cursor() as cursor:
        # 执行SQL查询
        sql = "SELECT * FROM users WHERE name = %s"
        cursor.execute(sql, ('John Doe',))
        result = cursor.fetchall()
        for row in result:
            print(row)

finally:
    connection.close()

插入数据：

import pymysql

# 连接MySQL数据库
connection = pymysql.connect(
    host='localhost',
    user='your_username',    # 替换为你的MySQL用户名
    password='your_password',  # 替换为你的MySQL密码
    db='your_database',      # 替换为你的数据库名称
    charset='utf8mb4',
    cursorclass=pymysql.cursors.DictCursor
)

try:
    with connection.cursor() as cursor:
        # 执行SQL插入
        sql = "INSERT INTO users (name, address, email) VALUES (%s, %s, %s)"
        cursor.execute(sql, ('John Doe', '123 Main St', 'john.doe@example.com'))
    
    # 提交事务
    connection.commit()

finally:
    connection.close()

数据更新：

import pymysql

# 连接MySQL数据库
connection = pymysql.connect(
    host='localhost',
    user='your_username',    # 替换为你的MySQL用户名
    password='your_password',  # 替换为你的MySQL密码
    db='your_database',      # 替换为你的数据库名称
    charset='utf8mb4',
    cursorclass=pymysql.cursors.DictCursor
)

try:
    with connection.cursor() as cursor:
        # 执行SQL更新
        sql = "UPDATE users SET address = %s WHERE name = %s"
        cursor.execute(sql, ('456 Oak St', 'John Doe'))
    
    # 提交事务
    connection.commit()

finally:
    connection.close()

删除数据：

import pymysql

# 连接MySQL数据库
connection = pymysql.connect(
    host='localhost',
    user='your_username',    # 替换为你的MySQL用户名
    password='your_password',  # 替换为你的MySQL密码
    db='your_database',      # 替换为你的数据库名称
    charset='utf8mb4',
    cursorclass=pymysql.cursors.DictCursor
)

try:
    with connection.cursor() as cursor:
        # 执行SQL删除
        sql = "DELETE FROM users WHERE name = %s"
        cursor.execute(sql, ('John Doe',))
    
    # 提交事务
    connection.commit()

finally:
    connection.close()

单字段查询：