- The number of rows in the result set of `INTERP` is determined by the parameter `EVERY(time_unit)`. Starting from timestamp1, one interpolation is performed for every time interval specified `time_unit` parameter. The parameter `time_unit` must be an integer, with no quotes, with a time unit of: a(millisecond)), s(second), m(minute), h(hour), d(day), or w(week). For example, `EVERY(500a)` will interpolate every 500 milliseconds.
- Interpolation is performed based on `FILL` parameter. For more information about FILL clause, see [FILL Clause](../distinguished/#fill-clause).
- `INTERP` can only be used to interpolate in single timeline. So it must be used with `partition by tbname` when it's used on a STable.
- Pseudocolumn `_irowts` can be used along with `INTERP` to return the timestamps associated with interpolation points(support after version 3.0.1.4).
- Pseudocolumn `_isfilled` can be used along with `INTERP` to indicate whether the results are original records or data points generated by interpolation algorithm(support after version 3.0.2.3).
- Pseudocolumn `_irowts` can be used along with `INTERP` to return the timestamps associated with interpolation points(support after version 3.0.2.0).
- Pseudocolumn `_isfilled` can be used along with `INTERP` to indicate whether the results are original records or data points generated by interpolation algorithm(support after version 3.0.3.0).
- After executing the above steps, the command-line will output the result of `nodejsChecker.js` connecting to the TDengine instance and performing a simple insert and query.
</TabItem>
<TabItem value="rest" label="REST connector">
After installing the TDengine client, use the `restChecker.js` program to verify that the current environment supports Node.js access to TDengine.
Verification in details:
- Create an installation test folder such as `~/tdengine-test`. Download the [restChecker.js source code](https://github.com/taosdata/TDengine/tree/3.0/docs/examples/node/restexample/restChecker.js) to your local.
- Execute the following command from the command-line.
```bash
npm init -y
npm install @tdengine/rest
node restChecker.js
```
- After executing the above steps, the command-line will output the result of `restChecker.js` connecting to the TDengine instance and performing a simple insert and query.
@@ -179,9 +179,10 @@ The parameters described in this document by the effect that they have on the sy
| Attribute | Description |
| -------- | -------------------------------- |
| Applicable | Server only |
| Meaning | count()/hyperloglog() return value or not if the result data is NULL |
| Meaning | count()/hyperloglog() return value or not if the input data is empty or NULL |
| Vlue Range | 0:Return empty line,1:Return 0 |
| Default | 1 |
| Notes | When this parameter is setting to 1, for queries containing GROUP BY, PARTITION BY and INTERVAL clause, and input data in certain groups or windows is empty or NULL, the corresponding groups or windows have no return values |
TDengine is a high-efficient, scalable, high-available distributed time-series database, which makes a lot of optimizations on inserting and querying data, which is far more efficient than normal regular databases. So TDengine can meet the high requirements of IOT and other areas on storing and querying a large amount of data.
TDengine is an open-source, cloud-native time-series database optimized for Internet of Things (IoT), Connected Cars, and Industrial IoT. With its built-in caching, stream processing, and data subscription capabilities, TDengine offers a simplified solution for time-series data processing.
To configure TDengine : edit /etc/taos/taos.cfg
To start service : launchctl start com.tdengine.taosd
TDengine is an open-source, cloud-native time-series database optimized for Internet of Things (IoT), Connected Cars, and Industrial IoT. With its built-in caching, stream processing, and data subscription capabilities, TDengine offers a simplified solution for time-series data processing.
Once it's installed, please take the steps below:
1: open a terminal/shell in Mac
2: if connecting to Cloud Service, follow the instructions on your cloud service account and configure the environment variable
3: if connecting to another TDengine Service, you can also view help information via "taos --help"