---
title: SQL selector functions
description: Select data with SQL selector functions.
url: https://docs.influxdata.com/influxdb3/clustered/reference/sql/functions/selector/
estimated_tokens: 1651
publisher: InfluxData
canonical: https://docs.influxdata.com/influxdb3/clustered/reference/sql/functions/selector/
date: '2025-09-05T08:26:38-06:00'
lastmod: '2025-09-05T08:26:38-06:00'
---

SQL selector functions are designed to work with time series data.
They behave similarly to aggregate functions in that they take a collection of
data and return a single value.
However, selectors are unique in that they return a *struct* that contains
a **time value** in addition to the computed value.

* [How do selector functions work?](#how-do-selector-functions-work)
* [Selector functions](#selector-functions)
  * [selector\_min](#selector_min)
  * [selector\_max](#selector_max)
  * [selector\_first](#selector_first)
  * [selector\_last](#selector_last)

## How do selector functions work?

Each selector function returns an [Arrow *struct*](https://arrow.apache.org/docs/format/Columnar.html#struct-layout)(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}
```

### Selector functions in use

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
```

## Selector functions

* [selector\_min](#selector_min)
* [selector\_max](#selector_max)
* [selector\_first](#selector_first)
* [selector\_last](#selector_last)

### selector\_min

Returns the smallest value of a selected column and a timestamp.

```sql
selector_min(expression, timestamp)
```

#### Arguments

* **expression**: Expression to operate on.
  Can be a constant, column, or function, and any combination of string or
  arithmetic operators.
* **timestamp**: Time expression.
  Can be a constant, column, or function.

[](#view-selector_min-query-example)

View `selector_min` query example

*The following example uses the[NOAA Bay Area weather sample data](/influxdb3/clustered/reference/sample-data/#noaa-bay-area-weather-data).*

```sql
SELECT
  location,
  selector_min(temp_min, time)['time'] AS time,
  selector_min(temp_min, time)['value'] AS min_temp
FROM
  weather
GROUP BY
  location
```

| location | time | min\_temp |
+—————+———————+———-+
| Concord | 2022-01-02T00:00:00 | 28.0 |
| Hayward | 2021-01-26T00:00:00 | 32.0 |
| San Francisco | 2022-01-02T00:00:00 | 35.0 |

### selector\_max

Returns the largest value of a selected column and a timestamp.

```sql
selector_max(expression, timestamp)
```

#### Arguments

* **expression**: Expression to operate on.
  Can be a constant, column, or function, and any combination of string or
  arithmetic operators.
* **timestamp**: Time expression.
  Can be a constant, column, or function.

[](#view-selector_max-query-example)

View `selector_max` query example

*The following example uses the[NOAA Bay Area weather sample data](/influxdb3/clustered/reference/sample-data/#noaa-bay-area-weather-data).*

```sql
SELECT
  location,
  selector_max(temp_max, time)['time'] AS time,
  selector_max(temp_max, time)['value'] AS max_temp
FROM
  weather
GROUP BY
  location
```

|  location   |       time        |max\_temp|
|-------------|-------------------|---------|
|   Concord   |2020-09-07T00:00:00|  112.0  |
|   Hayward   |2022-09-06T00:00:00|  107.0  |
|San Francisco|2020-09-06T00:00:00|  102.0  |

### selector\_first

Returns the first value ordered by time ascending.

```sql
selector_first(expression, timestamp)
```

#### Arguments

* **expression**: Expression to operate on.
  Can be a constant, column, or function, and any combination of string or
  arithmetic operators.
* **timestamp**: Time expression.
  Can be a constant, column, or function.

[](#view-selector_first-query-example)

View `selector_first` query example

*The following example uses the[NOAA Bay Area weather sample data](/influxdb3/clustered/reference/sample-data/#noaa-bay-area-weather-data).*

```sql
SELECT
  location,
  selector_first(precip, time)['time'] AS time,
  selector_first(precip, time)['value'] AS first_precip
FROM
  (SELECT * FROM weather WHERE precip > 0)
GROUP BY
  location
```

|  location   |       time        |first\_precip|
|-------------|-------------------|-------------|
|   Concord   |2020-01-08T00:00:00|    0.01     |
|   Hayward   |2020-01-09T00:00:00|    0.17     |
|San Francisco|2020-01-07T00:00:00|    0.03     |

### selector\_last

Returns the last value ordered by time ascending.

```sql
selector_last(expression, timestamp)
```

#### Arguments

* **expression**: Expression to operate on.
  Can be a constant, column, or function, and any combination of string or
  arithmetic operators.
* **timestamp**: Time expression.
  Can be a constant, column, or function.

[](#view-selector_last-query-example)

View `selector_last` query example

*The following example uses the[NOAA Bay Area weather sample data](/influxdb3/clustered/reference/sample-data/#noaa-bay-area-weather-data).*

```sql
SELECT
  location,
  selector_last(precip, time)['time'] AS time,
  selector_last(precip, time)['value'] AS last_precip
FROM
  (SELECT * FROM weather WHERE precip > 0)
GROUP BY
  location
```

|  location   |       time        |last\_precip|
|-------------|-------------------|------------|
|   Concord   |2022-12-31T00:00:00|    3.04    |
|   Hayward   |2022-12-31T00:00:00|    4.34    |
|San Francisco|2022-12-31T00:00:00|    3.67    |

#### Related

* [Aggregate data with SQL](/influxdb3/clustered/query-data/sql/aggregate-select/)
| location | time | max_temp |
| --- | --- | --- |
| location | time | max_temp |
| Concord | 2020-09-07T00:00:00 | 112.0 |
| Hayward | 2022-09-06T00:00:00 | 107.0 |
| San Francisco | 2020-09-06T00:00:00 | 102.0 |

| location | time | first_precip |
| --- | --- | --- |
| location | time | first_precip |
| Concord | 2020-01-08T00:00:00 | 0.01 |
| Hayward | 2020-01-09T00:00:00 | 0.17 |
| San Francisco | 2020-01-07T00:00:00 | 0.03 |

| location | time | last_precip |
| --- | --- | --- |
| location | time | last_precip |
| Concord | 2022-12-31T00:00:00 | 3.04 |
| Hayward | 2022-12-31T00:00:00 | 4.34 |
| San Francisco | 2022-12-31T00:00:00 | 3.67 |