MySQL chain of queries without loosing data

[Alexander Kirchner]

Hello,

How can i make a chain of decisions in node red without loosing the original information from the incomming MQTT data?

I want to write a parser, witch translate an incoming mqtt-data and write the data to a sql database if data is allowed.

First i splitt the mqtt-data into pieces.

Then i look into the database if one piece already exist to make the decisio if i can write the rest to the database.

But how can i make this with node-red?

After the SQL-Node i lost the data from the original MQTT-Data.
Is this possible?

Thank you

Alex.

[Mark Setrem]

as you found the nodes tend to place the interesting output in msg.payload over writing what was there.

If you want to retain the original msg.payload the trick is to move this to something else in the msg object e.g. msg.mqtt
This should then be retained through the flow.

You should be able to do this copy with a change node or a function node

[Garry Hayne]

Mark' suggestion is the easiest way:

Garry

[Alexander Kirchner]

Hi Guys THANK YOU. i ave to try this. I'm not the big coder, so i need a bit time.

[Alexander Kirchner]

The Picture again.

[Garry Hayne]

Alexander, can you show us the contents of the function node (SQL query), I suspect that you are not returning the msg object there.

Garry

On Sunday, February 18, 2018 at 12:24:35 PM UTC, Alexander Kirchner wrote:

The Picture again.

[Alexander Kirchner]

Sorry, but my Post with the code was deleted. (by google?)

var separator = msg.topic.split("/");

var temp0 = String(separator[0]);

var temp1 = String(separator[1]);

var temp2 = String(separator[2]);

var COT = {payload:temp0};

var CID = {payload:temp1};

var DIR = {payload:temp2};

var sqlstring = {

     topic: "SELECT connectors.id FROM connectors WHERE connector_uuid='"+temp1+"'"

 };

 

return sqlstring;

Thank you

Alex.

[Colin Law]

Instead of the last 5 lines do

msg.mqtt = msg.payload;

msg.topic = "SELECT connectors.id FROM connectors WHERE connector_uuid='"+temp1+"'"

return msg;

Then the original payload will still be available downstream in msg.mqtt, if that is what you are trying to achieve.

Colin

 

Thank you

Alex.

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[Alexander Kirchner]

Hello Colin Law!
you really saved my Weekend! That easy and that logic.

Thank you very much!
Alex.

[Zenofmud]

In your function node you are returning a new message (sqlstring) and not the original msg so of course the new msg will not have msg.mqtt set.

> On Feb 18, 2018, at 7:21 AM, Alexander Kirchner <ma...@alexanderkirchner.at> wrote:
>
> <payload_mqtt_chnge.jpg>

[Zenofmud]

Try changing that function to:
--------------------------

var separator = msg.topic.split("/");
var temp0 = String(separator[0]);
var temp1 = String(separator[1]);
var temp2 = String(separator[2]);
var COT = {payload:temp0};
var CID = {payload:temp1};
var DIR = {payload:temp2};

msg.topic = "SELECT connectors.id FROM connectors WHERE connector_uuid='"+temp1+"'";

return msg;

--------------------------