SQL语言如何在Python中执行查询 SQL语言与Python连接数据库的完整教程

sqlite3

psycopg2

pymysql

sqlite3

psycopg2

pymysql

mysql-connector-python

import sqlite3

# 连接到数据库 (如果数据库不存在，则会创建一个)
conn = sqlite3.connect('my_database.db')

# 创建一个游标对象
cursor = conn.cursor()

# 执行SQL语句 (创建表)
cursor.execute('''
CREATE TABLE IF NOT EXISTS users (
    id INTEGER PRIMARY KEY,
    name TEXT NOT NULL,
    age INTEGER
)
''')

# 插入数据
cursor.execute("INSERT INTO users (name, age) VALUES ('Alice', 30)")
cursor.execute("INSERT INTO users (name, age) VALUES ('Bob', 25)")

# 提交更改
conn.commit()

# 执行查询
cursor.execute("SELECT * FROM users")

# 获取查询结果
results = cursor.fetchall()

# 打印结果
for row in results:
    print(row)

# 关闭连接
conn.close()

conn.commit()

name = 'Charlie'
age = 35
cursor.execute("INSERT INTO users (name, age) VALUES (?, ?)", (name, age))
conn.commit()

?

sqlite3

psycopg2

pymysql

mysql-connector-python

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

# 创建一个数据库引擎 (以PostgreSQL为例)
engine = create_engine('postgresql://user:password@host:port/database', pool_size=5, max_overflow=10)

# 创建一个会话类
Session = sessionmaker(bind=engine)

# 使用会话
session = Session()
try:
    # 执行查询
    results = session.execute("SELECT * FROM users")
    for row in results:
        print(row)
except Exception as e:
    print(f"Error: {e}")
finally:
    session.close() # 归还连接到连接池

sqlalchemy

pool_size

max_overflow

try...except

try:
    cursor.execute("SELECT * FROM non_existent_table")
except sqlite3.Error as e:
    print(f"An error occurred: {e}")

sqlite3.Error