Question

我试图在Lambda（Python 3.6）中获取PyMySQL查询以返回用户是否存在。我将我的松弛用户ID传递给查询。这就是我想要在MySQL中检查的内容。我可以通过MySQL运行相同的查询，它返回0，但由于某种原因，每次我通过lambda调用此查询时，它告诉我用户存在（我的数据库为空）。我的查询功能就是：

def userExists(user):
    statement = f"SELECT EXISTS(SELECT 1 FROM slackDB.Assets WHERE userID LIKE '%{user}%')Assets"
    tempBool  = cursor.execute(statement, args=None) 
    conn.commit()
    return tempBool

以下是我正在使用的完整代码：

################################
# Slack Lambda handler.
################################

import sys
import logging
import os
import pymysql
import urllib

# Grab data from the environment.
BOT_TOKEN   = os.environ["BOT_TOKEN"]
ASSET_TABLE = os.environ["ASSET_TABLE"]
REGION_NAME = os.getenv('REGION_NAME', 'us-east-2')

DB_NAME     = "admin"
DB_PASSWORD = "somepassword"
DB_DATABASE = "someDB"
RDS_HOST    = "myslackdb.somepseudourl.us-east-2.rds.amazonaws.com"
port        = 3306

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

try:
    conn = pymysql.connect(RDS_HOST, user=DB_NAME, passwd=DB_PASSWORD, db=DB_DATABASE, connect_timeout=5)
    cursor = conn.cursor()
except:
    logger.error("ERROR: Unexpected error: Could not connect to MySql instance.")
    sys.exit()

# Define the URL of the targeted Slack API resource.
SLACK_URL = "https://slack.com/api/chat.postMessage"

def userExists(user):
    statement = f"SELECT EXISTS(SELECT 1 FROM slackDB.Assets WHERE userID LIKE '%{user}%')Assets"
    tempBool  = cursor.execute(statement, args=None) 
    conn.commit()
    return tempBool

def addUser(user):
    statement = f"INSERT INTO `slackDB`.`Assets` (`userID`, `money`) VALUES ('{user}', '1000')"
    tempBool  = cursor.execute(statement, args=None) 
    conn.commit()
    return tempBool

def lambda_handler(data, context):
    # Slack challenge answer.
    if "challenge" in data:
        return data["challenge"]

    # Grab the Slack channel data.
    slack_event    = data['event']
    slack_userID   = slack_event["user"]
    slack_text     = slack_event["text"]
    channel_id     = slack_event["channel"]
    slack_reply    = ""

    # Ignore bot messages.
    if "bot_id" in slack_event:
        slack_reply = ""
    else:
        # Start data sift.
        if slack_text.startswith("!networth"):
            slack_reply = "Your networth is: "
        elif slack_text.startswith("!price"):
            command,asset = text.split()
            slack_reply = f"The price of a(n) {asset} is: "
        elif slack_text.startswith("!addme"):
            if userExists(slack_userID):
                slack_reply = f"User {slack_userID} already exists"
            else:
                slack_reply = f"Adding user {slack_userID}"
                addUser(slack_userID)

        # We need to send back three pieces of information:
        data = urllib.parse.urlencode(
            (
                ("token", BOT_TOKEN),
                ("channel", channel_id),
                ("text", slack_reply)
            )
        )
        data = data.encode("ascii")

        # Construct the HTTP request that will be sent to the Slack API.
        request = urllib.request.Request(
            SLACK_URL, 
            data=data, 
            method="POST"
        )
        # Add a header mentioning that the text is URL-encoded.
        request.add_header(
            "Content-Type", 
            "application/x-www-form-urlencoded"
        )

        # Fire off the request!
        urllib.request.urlopen(request).read()

    # Everything went fine.
    return "200 OK"

我在松弛中键入'！addme'，它总是告诉我用户存在。我打印出我的查询语句，它正在输入我的松弛ID。我检查了我的桌子，它完全是空的。我在MySQL中运行了查询，它返回0。

有没有人有任何想法？我只是简单易懂吗？任何帮助或提示都非常感谢。

谢谢，

Answer 1

我没有从光标看到fetch。只是execute。

execute的回报是受影响的行数。对于有意义的DML操作（INSERT / UPDATE / DELETE）。但我不会依赖SELECT的行数。

在这种情况下，SELECT EXISTS查询将返回一行，或者抛出错误。但是查询返回行的事实并没有告诉我们Assets列的值。

从查询中，看起来我们想要获取一行，然后确定Assets列是否包含0或1（或NULL）。

执行查询后，请尝试cur.fetchone检索该行。

我们还可以执行更简单的查询，然后使用fetch来确定是否返回了一行。

Lambda（Python 3.6）PyMySql查询EXISTS查询始终返回1

1 个答案: