我如何使用python3将值插入sql表？

Question

Moin！

我正在尝试使用paho库建立mqtt客户端。这样就没有问题，但是我试图将收到的发布内容插入sql数据库中。我将收到的有效负载字符串转换为字典，并添加一些条目。执行以下代码时：

def insert_values(db_connection=None, topic=None, payload=None, time_received=None):
    query_1 = "SELECT topic_id FROM topics WHERE topic = %s"
    query_2 = """INSERT INTO measurements (start_time, end_time, value, max_value, min_value, time_received, topic_id)
                 VALUES (%(start_time)s, %(end_time)s, %(value)s, %(max_value)s, %(min_value)s, %(time_received)s, 
                        %(topic_id)s)"""
    cursor = db_connection.cursor(prepared=True)
    topic_id = cursor.execute(query_1, topic)
    payload["time_received"] = time_received
    payload["topic_id"] = topic_id
    cursor.executemany(query_2, payload)
    db_connection.commit()
    db_disconnect(db_connection, cursor)

我收到以下错误：

Caught exception in on_message: 1210: Incorrect number of arguments executing prepared statement

负载看起来像这样：

payload = {
        "Starttime:": 2020-02-18 10:11:22.2145563,
        "Endtime:": 2020-02-18 10:12:22.2145563,
        "Average Humidity:": 44.256241,
        "Number of Values:": 22,
        "Max Humidity:": 44.586214,
        "Min Humidity:": 44.012148521)
}

加上一些其他信息，例如接收有效负载的时间。在insert_values方法中，我试图从表主题中获取topic_id并将其写入有效负载。

感谢您的提示！

编辑：要在其中写入测量值的表如下所示：

CREATE TABLE IF NOT EXISTS measurements
(measurement_id INT AUTO_INCREMENT,
 start_time DATETIME,
 end_time DATETIME,
 value FLOAT,
 max_value FLOAT,
 min_value FLOAT,
 time_received DATETIME,
 topic_id INT,
 PRIMARY KEY (measurement_id),
 FOREIGN KEY (topic_id) REFERENCES topics(topic_id))

Answer 1

您的有效负载有6个键，然后再添加2个键，使其成为8您的查询中只有7个参数我不确定，但我认为您忘记添加“平均湿度”编辑：看到您的表DESC

    query_2 = """INSERT INTO measurements (start_time, end_time, value, max_value, min_value, time_received, topic_id)
             VALUES (%s,%s,%s,%s,%s,%s,%s)"""
cursor = db_connection.cursor(prepared=True)
topic_id = cursor.execute(query_1, topic)
payload["time_received"] = time_received
payload["topic_id"] = topic_id
payload.pop("Average Humidity:", None)
cursor.executemany(query_2, payload)
db_connection.commit()
db_disconnect(db_connection, cursor)

Answer 2

这里：

"""VALUES (%(start_time)s, %(end_time)s, %(value)s, %(max_value)s, %(min_value)s, %(time_received)s, %(topic_id)s)"""

和这里：

payload = {
    "Starttime:": 2020-02-18 10:11:22.2145563,
    "Endtime:": 2020-02-18 10:12:22.2145563,
    "Average Humidity:": 44.256241,
    "Number of Values:": 22,
    "Max Humidity:": 44.586214,
    "Min Humidity:": 44.012148521)
}

您的payload键必须与查询的占位符名称匹配-或您的占位符与payload键匹配。您的数据库客户端肯定不会尝试猜测“ start_time”和“ Starttime”实际上是同一回事。当然，您必须具有all查询占位符的数学键。