ISSUE with storing MQTT values to mySQL database : the values store as "undefined". Any guidence is much appreciated


INSERT INTO readingsreceived(ssid,rssi,scan_mac,sensor_mac)VALUES('undefined','NaN','undefined','undefined'); : msg.payload : ResultSetHeader

"[object Object]"


ssid = msg.payload.ssid;
rssi = parseInt(msg.payload.rssi);
scan_mac = msg.payload.scan_mac;
sensor_mac = msg.payload.sensor_mac;

insert = "INSERT INTO readingsreceived(ssid,rssi,scan_mac,sensor_mac)" +

msg.topic = insert;
return msg;

Firstly, welcome to the forum. However, could you please read up on how to include code in a post? Thanks, it makes things much easier to read.

Now to your problem. The flow you've shown doesn't quite do what you think. Those separate change nodes all need to be in a single node because the result of your current flow is that you are sending 4 separate messages to the function node with each message only containing a single value not all of them as you are assuming.

A couple of other points. You can use back-tick quotes in your insert to make things rather easier to read:

insert = `INSERT INTO readingsreceived(ssid,rssi,scan_mac,sensor_mac) VALUES("${ssid}", "${rssi}", "${scan_mac}", "${sensor_mac}")`

Secondly, it is wise to use a "prepared statement" rather than a manually constructed insert statement. Those are more efficient but more importantly, they are less susceptible to SQL attacks.

Hi, thank you for the prompt response, sorry about the delay to reply. So as you suggested I started with bringing all four change node values to one node, But I am getting an error.

What does the data coming from your json node look like - is it one message with all four elements in it, or do they arrive as four seperate messages?

This is the problem...

The thing is - you dont even need to do this at all!

The better solution...

In your function where you build the query, simply use :named_parameters and the values will be picked out of the payload...

msg.payload.rssi = parseInt(msg.payload.rssi);
msg.topic = "INSERT INTO readingsreceived(ssid,rssi,scan_mac,sensor_mac) VALUES (:ssid,:rssi,:scan_mac,:sensor_mac);"
return msg;

REF: See the readme, section "Prepared Queries".

Added bonus for free

Using prepared statements will also help you avoid SQL injection issues.


It's a JSON, where the key and value are identified and highlighted. slightly different to what you see in the debug window in the image I have shown.

Hey Steve, your solution worked , thank you very much. For my knowledge please elaborate what was actually happening to the values , as in why were they not going to the database.

Since all the related data arrives in a single message, as Steve says, you don't need the change node at all.

And you may not need the json node, if your mqtt-in is set to receive a parsed JSON object (depending what else is connected to mqtt-in)

I still used the JSON node , but did away with the change nodes. Its working fine now, thanks for helping out.

Did this not make sense :point_down:

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