---
title: Aggregate or apply selector functions to data
description: Use aggregate and selector functions to perform aggregate operations on your time series data.
url: https://docs.influxdata.com/influxdb3/cloud-dedicated/query-data/sql/aggregate-select/
estimated_tokens: 2782
publisher: InfluxData
canonical: https://docs.influxdata.com/influxdb3/cloud-dedicated/query-data/sql/aggregate-select/
date: '2025-03-13T17:02:04-06:00'
lastmod: '2025-03-13T17:02:04-06:00'
---

An SQL query that aggregates data includes the following clauses:

\* Required

* \* `SELECT`: Specify fields, tags, and calculations to output from a
  measurement or use the wildcard alias (`*`) to select all fields and tags
  from a measurement.
* \* `FROM`: Specify the measurement to query data from.
* `WHERE`: Only return data that meets the specified conditions–for example, falls within
  a time range, contains specific tag values, or contains a field value outside a specified range.
* `GROUP BY`: Group data that have the same values for specified columns and expressions (for example, an aggregate function result).

> [!Note]
> For simplicity, the term **“aggregate”** in this guide refers to applying
> both aggregate and selector functions to a dataset.

Learn how to apply aggregate operations to your queried data:

* [Aggregate and selector functions](#aggregate-and-selector-functions)
  * [Aggregate functions](#aggregate-functions)
  * [Selector functions](#selector-functions)

* [Example aggregate queries](#example-aggregate-queries)

## Aggregate and selector functions

Both aggregate and selector functions return a single row from each SQL partition
or group. For example, if you `GROUP BY room` and perform an aggregate operation
in your `SELECT` clause, results include an aggregate value for each unique
value of `room`.

### Aggregate functions

Use **aggregate functions** to aggregate values in a specified column for each
group and return a single row per group containing the aggregate value.

[View aggregate functions](/influxdb3/cloud-dedicated/reference/sql/functions/aggregate/)

##### Basic aggregate query

```sql
SELECT AVG(co) from home
```

### Selector functions

Use **selector functions** to “select” a value from a specified column.
The available selector functions are designed to work with time series data.

[View selector functions](/influxdb3/cloud-dedicated/reference/sql/functions/selector/)

Each selector function returns a Rust *struct* (similar to a JSON object)
representing a single time and value from the specified column in the each group.
What time and value get returned depend on the logic in the selector function.
For example, `selector_first` returns the value of specified column in the first row of the group.`selector_max` returns the maximum value of the specified column in the group.

#### Selector struct schema

The struct returned from a selector function has two properties:

* **time**: `time` value in the selected row
* **value**: value of the specified column in the selected row

```js
{time: 2023-01-01T00:00:00Z, value: 72.1}
```

#### Use selector functions

Each selector function has two arguments:

* The first is the column to operate on.
* The second is the time column to use in the selection logic.

In your `SELECT` statement, execute a selector function and use bracket notation
to reference properties of the [returned struct](#selector-struct-schema) to
populate the column value:

```sql
SELECT
  selector_first(temp, time)['time'] AS time,
  selector_first(temp, time)['value'] AS temp,
  room
FROM home
GROUP BY room
```

## Example aggregate queries

* [Perform an ungrouped aggregation](#perform-an-ungrouped-aggregation)
* [Group and aggregate data](#group-and-aggregate-data)
  * [Downsample data by applying interval-based aggregates](#downsample-data-by-applying-interval-based-aggregates)

* [Query rows based on aggregate values](#query-rows-based-on-aggregate-values)

#### Sample data

The following examples use the sample data written in the[Get started writing data guide](/influxdb3/cloud-dedicated/get-started/write/).
To run the example queries and return results,[write the sample data](/influxdb3/cloud-dedicated/get-started/write/#write-line-protocol-to-influxdb)to your InfluxDB Cloud dedicated database before running the example queries.

### Perform an ungrouped aggregation

To aggregate *all* queried values in a specified column:

* Use aggregate or selector functions in your `SELECT` statement.
* Do not include a `GROUP BY` clause to leave your data ungrouped.

```sql
SELECT avg(co) AS 'average co' from home
```

[](#view-example-results)

View example results

|   average co    |
|-----------------|
|5.269230769230769|

### Group and aggregate data

To apply aggregate or selector functions to grouped data:

* Use aggregate or selector functions in your `SELECT` statement.
* Include columns to group by in your `SELECT` statement.
* Include a `GROUP BY` clause with a comma-delimited list of columns and expressions to group by.

Keep the following in mind when using `GROUP BY`:

* `GROUP BY` can use column aliases that are defined in the `SELECT` clause.
* `GROUP BY` can’t use an alias named `time`. If you include `time` in `GROUP BY`, it always uses the measurement `time` column.

```sql
SELECT
  room,
  avg(temp) AS 'average temp'
FROM home
GROUP BY room
```

[](#view-example-results)

View example results

|   room    |   average temp   |
|-----------|------------------|
|Living Room|22.16923076923077 |
|  Kitchen  |22.623076923076926|

#### Downsample data by applying interval-based aggregates

A common use case when querying time series is downsampling data by applying
aggregates to time-based groups. To group and aggregate data into time-based
groups:

* In your `SELECT` clause:

  * Use the [`DATE_BIN` function](/influxdb3/cloud-dedicated/reference/sql/functions/time-and-date/#date_bin)to calculate time intervals and output a column that contains the start of the interval nearest to the `time` timestamp in each row–for example,
    the following clause calculates two-hour intervals starting at `1970-01-01T00:00:00Z` and returns a new `time` column that contains the start of the interval
    nearest to `home.time`:

    ```
    SELECT
      DATE_BIN(INTERVAL '2 hours', time, '1970-01-01T00:00:00Z') AS time
    FROM home
    ...
    ```

    Given a `time` value`2023-03-09T13:00:50.000Z`,
    the output `time` column contains`2023-03-09T12:00:00.000Z`.

  * Use [aggregate](/influxdb3/cloud-dedicated/reference/sql/functions/aggregate/) or [selector](/influxdb3/cloud-dedicated/reference/sql/functions/selector/) functions on specified columns.

* In your `GROUP BY` clause:

  * Specify the `DATE_BIN(...)` column ordinal reference (`1`).
  * Specify other columns (for example, `room`) that are specified in the `SELECT` clause and aren’t used in a selector function.

  ```
  SELECT
    DATE_BIN(INTERVAL '2 hours', time, '1970-01-01T00:00:00Z') AS time
  ...
  GROUP BY 1, room
  ...
  ```

  To reference the `DATE_BIN(...)` result column by *name* in the `GROUP BY` clause, assign an alias other than “time” in the `SELECT` clause–for example:

  ```
  SELECT
    DATE_BIN(INTERVAL '2 hours', time, '1970-01-01T00:00:00Z') AS _time
  FROM home
  ...
  GROUP BY _time, room
  ```

* Include an `ORDER BY` clause with columns to sort by.

The following example retrieves unique combinations of time intervals and rooms with their minimum, maximum, and average temperatures.

```sql
SELECT
  DATE_BIN(INTERVAL '2 hours', time, '1970-01-01T00:00:00Z') AS time,
  room,
  selector_max(temp, time)['value'] AS 'max temp',
  selector_min(temp, time)['value'] AS 'min temp',
  avg(temp) AS 'average temp'
FROM home
GROUP BY 1, room
ORDER BY room, 1
```

[](#view-example-results)

View example results

|        time        |   room    |max temp|min temp|   average temp   |
|--------------------|-----------|--------|--------|------------------|
|2022-01-01T08:00:00Z|  Kitchen  |   23   |   21   |        22        |
|2022-01-01T10:00:00Z|  Kitchen  |  22.7  |  22.4  |22.549999999999997|
|2022-01-01T12:00:00Z|  Kitchen  |  22.8  |  22.5  |      22.65       |
|2022-01-01T14:00:00Z|  Kitchen  |  22.8  |  22.7  |      22.75       |
|2022-01-01T16:00:00Z|  Kitchen  |  22.7  |  22.4  |22.549999999999997|
|2022-01-01T18:00:00Z|  Kitchen  |  23.3  |  23.1  |23.200000000000003|
|2022-01-01T20:00:00Z|  Kitchen  |  22.7  |  22.7  |       22.7       |
|2022-01-01T08:00:00Z|Living Room|  21.4  |  21.1  |      21.25       |
|2022-01-01T10:00:00Z|Living Room|  22.2  |  21.8  |        22        |
|2022-01-01T12:00:00Z|Living Room|  22.4  |  22.2  |22.299999999999997|
|2022-01-01T14:00:00Z|Living Room|  22.3  |  22.3  |       22.3       |
|2022-01-01T16:00:00Z|Living Room|  22.6  |  22.4  |       22.5       |
|2022-01-01T18:00:00Z|Living Room|  22.8  |  22.5  |      22.65       |
|2022-01-01T20:00:00Z|Living Room|  22.2  |  22.2  |       22.2       |

#### GROUP BY time

In the `GROUP BY` clause, the name “time” always refers to the `time` column in the source table.
If you want to reference a calculated time column by name, use an alias different from “time”–for example:

```sql
SELECT
  DATE_BIN(INTERVAL '2 hours', time, '1970-01-01T00:00:00Z')
  AS _time,
  room,
  selector_max(temp, time)['value'] AS 'max temp',
  selector_min(temp, time)['value'] AS 'min temp',
  avg(temp) AS 'average temp'
FROM home
GROUP BY _time, room
ORDER BY room, _time
```

### Query rows based on aggregate values

To query data based on values after an aggregate operation, include a `HAVING`clause with defined predicate conditions such as a value threshold.
Predicates in the `WHERE` clause are applied *before* data is aggregated.
Predicates in the `HAVING` clause are applied *after* data is aggregated.

```sql
SELECT
  room,
  avg(co) AS 'average co'
FROM home
GROUP BY room
HAVING "average co" > 5
```

[](#view-example-results)

View example results

| room  |    average co    |
|-------|------------------|
|Kitchen|6.6923076923076925|

#### Related

* [SQL aggregate functions](/influxdb3/cloud-dedicated/reference/sql/functions/aggregate/)
* [SQL selector functions](/influxdb3/cloud-dedicated/reference/sql/functions/selector/)
| average co |
| --- |
| average co |
| 5.269230769230769 |

| room | average temp |
| --- | --- |
| room | average temp |
| Living Room | 22.16923076923077 |
| Kitchen | 22.623076923076926 |

| time | room | max temp | min temp | average temp |
| --- | --- | --- | --- | --- |
| time | room | max temp | min temp | average temp |
| 2022-01-01T08:00:00Z | Kitchen | 23 | 21 | 22 |
| 2022-01-01T10:00:00Z | Kitchen | 22.7 | 22.4 | 22.549999999999997 |
| 2022-01-01T12:00:00Z | Kitchen | 22.8 | 22.5 | 22.65 |
| 2022-01-01T14:00:00Z | Kitchen | 22.8 | 22.7 | 22.75 |
| 2022-01-01T16:00:00Z | Kitchen | 22.7 | 22.4 | 22.549999999999997 |
| 2022-01-01T18:00:00Z | Kitchen | 23.3 | 23.1 | 23.200000000000003 |
| 2022-01-01T20:00:00Z | Kitchen | 22.7 | 22.7 | 22.7 |
| 2022-01-01T08:00:00Z | Living Room | 21.4 | 21.1 | 21.25 |
| 2022-01-01T10:00:00Z | Living Room | 22.2 | 21.8 | 22 |
| 2022-01-01T12:00:00Z | Living Room | 22.4 | 22.2 | 22.299999999999997 |
| 2022-01-01T14:00:00Z | Living Room | 22.3 | 22.3 | 22.3 |
| 2022-01-01T16:00:00Z | Living Room | 22.6 | 22.4 | 22.5 |
| 2022-01-01T18:00:00Z | Living Room | 22.8 | 22.5 | 22.65 |
| 2022-01-01T20:00:00Z | Living Room | 22.2 | 22.2 | 22.2 |

| room | average co |
| --- | --- |
| room | average co |
| Kitchen | 6.6923076923076925 |