Store IOT Data in SQLite Database in Node-Red

 Store IOT Data in SQLite Database  Node-Red

儲存物聯網資料使用SQLite資料庫節點元件

參考來源 http://www.steves-internet-guide.com/storing-iot-data-sql-database/

var n1 = Math.round( Math.random() *100)

var n2 = Math.round( Math.random() *100)

var n3 = Math.round( Math.random() *100)

var sensor="sensor"+n1;

msg="( timestamp,sensor,temperature,humidity) values(" + "\'"+ n1 +"\'"+",\'"+sensor +"\'" +",\'"+ n2 +"\'"+",\'" +n3 + "\'"+")";

var topic="INSERT INTO DATA " +msg;

var msg1={};

msg1.topic=topic;

return msg1;

JSON encoded data is also a text string and so can also be stored directly in the database, but more commonly you will want to extract parts of the data to use as database keys (column names).

The easiest way to see this is by doing an example. Let’s assume our incoming data payload looked like this:

sensor1,temperature,20,humidity,71

So what we have is a device called sensor1 and two key/value pairs:

temperature=20 and humidity=71

To store this data in a data base we first need a database and a table.

So lets create a database called test.db and a table called sensor_data.

Now a table consists of rows and columns. To create a row we need to add elements to the columns. To do that we need to assign names to the columns.

In our example we would need three columns called:

• sensor
• temperature
• humidity

We also need to assign a data type to the values, in our case sensor would be TEXT and temperature and humidity would be Integers (INT)

When we add our data to the table the table would look like this:

Sensor	Temperature	Humidity
sensor1	20	71

Note: Column names are not case sensitive.

The following code snippet shows how we do this:

var data="sensor1,temperature,20,humidity,71";
//extract elements from data
var sensor=data[0];
var temperature=data[3];
var humidity=data[5];

//create SQL command
msg="(sensor,temperature,humidity) values("+",\'"+sensor +"\'," + temperature + "," + humidity +")";
var topic="INSERT INTO DATA " +msg;
var msg1={}; //create new msg object
//The SQlite node expects the command in the topic field
msg1.topic=topic;
return msg1;

The interesting and most important point when  constructing the command is that text values need to be in quotes, and because we are constructing a string we need to escape them. So we have:

var n1 = Math.round( Math.random() *100)

var n2 = Math.round( Math.random() *100)

var n3 = Math.round( Math.random() *100)

var sensor="sensor"+n1;

msg="( timestamp,sensor,temperature,humidity) values(" + "\'"+ n1 +"\'"+",\'"+sensor +"\'" +",\'"+ n2 +"\'"+",\'" +n3 + "\'"+")";

var topic="INSERT INTO DATA " +msg;

var msg1={};

msg1.topic=topic;

return msg1;

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