86 lines
2.3 KiB
Markdown
86 lines
2.3 KiB
Markdown
---
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title: count() function
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description: The `count()` function outputs the number of non-null records in a column.
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aliases:
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- /influxdb/v2.0/reference/flux/functions/transformations/aggregates/count
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- /influxdb/v2.0/reference/flux/functions/built-in/transformations/aggregates/count/
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- /influxdb/v2.0/reference/flux/stdlib/built-in/transformations/aggregates/count/
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- /influxdb/cloud/reference/flux/stdlib/built-in/transformations/aggregates/count/
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menu:
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flux_0_x_ref:
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name: count
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parent: universe
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weight: 102
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flux/v0.x/tags: [aggregates, transformations]
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related:
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- /{{< latest "influxdb" "v1" >}}/query_language/functions/#count, InfluxQL – COUNT()
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- /flux/v0.x/stdlib/experimental/count/
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introduced: 0.7.0
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---
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The `count()` function outputs the number of records in a column.
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It counts both null and non-null records.
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_`count()` is an [aggregate function](/flux/v0.x/function-types/#aggregates)._
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_**Output data type:** Integer_
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```js
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count(column: "_value")
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```
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{{% note %}}
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#### Empty tables
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`count()` returns `0` for empty tables.
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To keep empty tables in your data, set the following parameters for the following functions:
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| Function | Parameter |
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| :--------------------------------------------------------------- | :------------------ |
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| [filter()](/flux/v0.x/stdlib/universe/filter/) | `onEmpty: "keep"` |
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| [window()](/flux/v0.x/stdlib/universe/window/) | `createEmpty: true` |
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| [aggregateWindow()](/flux/v0.x/stdlib/universe/aggregatewindow/) | `createEmpty: true` |
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{{% /note %}}
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## Parameters
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### column {data-type="string"}
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The column on which to operate.
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Defaults to `"_value"`.
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### tables {data-type="stream of tables"}
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Input data.
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Default is piped-forward data ([`<-`](/flux/v0.x/spec/expressions/#pipe-expressions)).
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## Examples
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{{% flux/sample-example-intro %}}
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#### Count the number of rows in each input table
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```js
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import "sampledata"
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sampledata.string()
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|> count()
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```
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{{% expand "View input and output" %}}
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{{< flex >}}
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{{% flex-content %}}
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##### Input data
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{{% flux/sample "string" %}}
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{{% /flex-content %}}
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{{% flex-content %}}
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##### Output data
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| tag | _value |
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| :-- | -----: |
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| t1 | 6 |
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| tag | _value |
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| :-- | -----: |
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| t2 | 6 |
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{{% /flex-content %}}
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{{< /flex >}}
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{{% /expand %}}
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