Python - 将 MySQL 选择查询结果导出到 CSV

Question

我正在尝试导出 MySQL 选择查询结果到 CSV 文件。

我为此使用 lambda，我的数据库在 RDS 中。

我可以连接并运行查询。

但是当我尝试将选择查询结果保存为 CSV 格式时，它不起作用。

需要 python 开发人员帮助编写此脚本。

注意：Unicodewritter 不适用于 lambda。

Lambda 函数：

import sys
import logging
import rds_config
import pymysql
#rds settings
rds_host  = "connection_link"
name = rds_config.db_username
password = rds_config.db_password
db_name = rds_config.db_name


logger = logging.getLogger()
logger.setLevel(logging.INFO)

try:
    conn = pymysql.connect(rds_host, user=name, passwd=password, db=db_name, connect_timeout=5)
except:
    logger.error("ERROR: Unexpected error: Could not connect to MySql instance.")
    sys.exit()

logger.info("SUCCESS: Connection to RDS mysql instance succeeded")

def handler(event, context):
    """
    This function fetches content from mysql RDS instance
    """

    item_count = 0

    with conn.cursor() as cur:
        cur.execute("create table Employee3 ( EmpID  int NOT NULL, Name varchar(255) NOT NULL, PRIMARY KEY (EmpID))")  
        cur.execute('insert into Employee3 (EmpID, Name) values(1, "Joe")')
        cur.execute('insert into Employee3 (EmpID, Name) values(2, "Bob")')
        cur.execute('insert into Employee3 (EmpID, Name) values(3, "Mary")')
        conn.commit()
        cur.execute("select * from Employee3")

        for row in cur:
            item_count += 1
            logger.info(row)
            #print(row)

Answer 1

以下标准方法应该可以写入所有行：

with conn.cursor() as cur:
    cur.execute("create table Employee3 ( EmpID  int NOT NULL, Name varchar(255) NOT NULL, PRIMARY KEY (EmpID))")  
    cur.execute('insert into Employee3 (EmpID, Name) values(1, "Joe")')
    cur.execute('insert into Employee3 (EmpID, Name) values(2, "Bob")')
    cur.execute('insert into Employee3 (EmpID, Name) values(3, "Mary")')
    conn.commit()
    cur.execute("select * from Employee3")

    res = cur.fetchall()
    with open('output.csv','w') as fileout:
        writer = csv.writer(fileout)
        writer.writerows(res)        

如果需要逐行处理，可以使用writerow 代替：

    cur.execute("select * from Employee3")

    with open('output.csv','w') as fileout:
        writer = csv.writer(fileout)
        for row in cur:
            writer.writerow(row)