Hello everyone, I am trying to link the RFID card detected from my MFRC RC522 card reader to link with the database created on phpMydmin. I have used MYSQL node and it successfully detects the database but when I am sending a query to read only the data related with the particular tag detected, it…

Your function node has two outputs, please use only one directly linked to the database node and try again :wink: (I mean, you have to actually set the number of outputs to 1 again. Using multiple outputs is not needed here)

Add a debug node which is set to show complete message and feed it with the message you are sending to the mysql node, there you will be able to see the query it is asking for.

Thanks @Colin for your reply, I had a debug node after my sql node and it reads SELECT ITEM FROM TAG_READ WHERE uID = 'context.data.uID' : msg.payload : array[0] [ empty ] FYI: TAG_READ is the table from my database uID is the column name on my database, which I want to equate with the context.d…

Is your SQL statement in msg.query or msg.payload? (a copy of the debug would have answered this question) I'm not sure you can reference context data in the query.

Thanks @zenofmud for your response, I am fetching my data from altairsmartcore via MQTT (context.data.uID), so I have initially one MQTT listening node on my node red, it receives data in msg.payload, then I have connected one function node which I am yet to figure out what to write in it to extract…

That would be much of work, I actually thought I could just let it link with my uID in the database and it could fetch the data related with uID.

You have to put the id in the select query. When you say context.data.uID what exactly do you mean by that? Have you put it into the node-red context or what?

By context.data.uID, I mean the TagID which I am receiving from Altairsmartcore via MQTT node. I want to relate that context.data.uID with the uID column of my database. So that it understands that when msg.topic = "SELECT * FROM TAG_READ WHERE uID = 'context.data.uID'"; return msg; It should ret…

Show us what you are getting out of the MQTT node.

To help us understand what's going on, it would be helpful if you provided your frow from where you get the data from the MQTT node to where you are making the MySQL call.

Node-RED

Node-RED Forum

Query to extract data from MariaDB using SELECT statement to link with the RFID card detected

General

Colin 9 October 2019 10:11 5

As @zenofmud says, you need to put the actual uiD value into the select string. Mysql cannot look in the node-red context.

1 Like

Topic		Replies	Views
Connection with database error General	115	2858	3 August 2020
Read from mysql db Dashboard	54	17580	23 December 2018
I have some questions relating database General	57	3707	3 December 2018
Generate SQL statement from 2 mqtt messages General	42	1083	20 July 2020
Copying my Door control status back to my Mysql databse General	96	1884	4 August 2020

Copyright OpenJS Foundation and Node-RED contributors. All rights reserved. The OpenJS Foundation has registered trademarks and uses trademarks. For a list of trademarks of the OpenJS Foundation, please see our Trademark Policy and Trademark List. Trademarks and logos not indicated on the list of OpenJS Foundation trademarks are trademarks™ or registered® trademarks of their respective holders. Use of them does not imply any affiliation with or endorsement by them.

Query to extract data from MariaDB using SELECT statement to link with the RFID card detected

Related topics