sql与 连接到服务器失败怎么办

ping <服务器IP地址>

# 对于MySQL
sudo systemctl status mysql

# 对于PostgreSQL
sudo systemctl status postgresql

# 对于Linux系统
sudo ufw allow <数据库端口>

# 示例：Python使用pymysql连接MySQL
import pymysql

connection = pymysql.connect(
    host='服务器IP地址',
    user='用户名',
    password='密码',
    db='数据库名',
    charset='utf8mb4',
    cursorclass=pymysql.cursors.DictCursor
)

import pymysql

try:
    connection = pymysql.connect(
        host='127.0.0.1',
        user='myuser',
        password='mypassword',
        db='mydatabase',
        charset='utf8mb4',
        cursorclass=pymysql.cursors.DictCursor
    )

    with connection.cursor() as cursor:
        sql = "SELECT * FROM mytable"
        cursor.execute(sql)
        result = cursor.fetchall()
        print(result)

finally:
    connection.close()