---
title: Check if a value exists
description: Use the Flux exists operator to check if a record contains a key or if that key’s value is null.
url: https://docs.influxdata.com/enterprise_influxdb/v1/flux/guides/exists/
estimated_tokens: 2065
product: InfluxDB Enterprise v1
version: v1
---

# Check if a value exists

Use the Flux `exists` operator to check if a record contains a key or if that key’s value is `null`.

```js
p = {firstName: "John", lastName: "Doe", age: 42}

exists p.firstName
// Returns true

exists p.height
// Returns false

```

If you’re just getting started with Flux queries, check out the following:

-   [Get started with Flux](/enterprise_influxdb/v1/flux/get-started/) for a conceptual overview of Flux and parts of a Flux query.
-   [Execute queries](/enterprise_influxdb/v1/flux/guides/execute-queries/) to discover a variety of ways to run your queries.

Use `exists` with row functions ( [`filter()`](/flux/v0/stdlib/universe/filter/), [`map()`](/flux/v0/stdlib/universe/map/), [`reduce()`](/flux/v0/stdlib/universe/reduce/)) to check if a row includes a column or if the value for that column is `null`.

#### Filter null values

```js
from(bucket: "db/rp")
    |> range(start: -5m)
    |> filter(fn: (r) => exists r._value)
```

#### Map values based on existence

```js
from(bucket: "default")
    |> range(start: -30s)
    |> map(
        fn: (r) => ({r with
            human_readable: if exists r._value then
                "${r._field} is ${string(v: r._value)}."
            else
                "${r._field} has no value.",
        }),
    )
```

#### Ignore null values in a custom aggregate function

```js
customSumProduct = (tables=<-) => tables
    |> reduce(
        identity: {sum: 0.0, product: 1.0},
        fn: (r, accumulator) => ({r with
            sum: if exists r._value then
                r._value + accumulator.sum
            else
                accumulator.sum,
            product: if exists r._value then
                r.value * accumulator.product
            else
                accumulator.product,
        }),
    )
```