---
title: SQL selector functions
description: Select data with SQL selector functions.
url: https://docs.influxdata.com/influxdb3/cloud-dedicated/reference/sql/functions/selector/
estimated_tokens: 4951
product: InfluxDB Cloud Dedicated
version: cloud-dedicated
---

# SQL selector functions

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/cloud-dedicated/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/cloud-dedicated/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/cloud-dedicated/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/cloud-dedicated/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 or apply selector functions to data](/influxdb3/cloud-dedicated/query-data/sql/aggregate-select/)