docs-v2/content/flux/v0/get-started/_index.md

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Flux is a functional data scripting language designed to unify querying, processing, analyzing, and acting on data into a single syntax.

Flux overview

To understand how Flux works conceptually, consider the process of treating water. Water is pulled from a source, limited by demand, piped through a series of stations to modify (remove sediment, purify, and so on), and delivered in a consumable state.

Basic Flux query

Like treating water, a Flux query does the following:

1. Retrieves a specified amount of data from a source.
2. Filters data based on time or column values.
3. Processes and shapes data into expected results.
4. Returns the result.

To see how to retrieve data from a source, select the data source: InfluxDB, CSV, or PostgreSQL.

{{< code-tabs-wrapper >}} {{% code-tabs %}} InfluxDB CSV PostgreSQL {{% /code-tabs %}} {{% code-tab-content %}}

from(bucket: "example-bucket")
    |> range(start: -1d)
    |> filter(fn: (r) => r._measurement == "example-measurement")
    |> mean()
    |> yield(name: "_results")

{{% /code-tab-content %}} {{% code-tab-content %}}

import "csv"

csv.from(file: "path/to/example/data.csv")
    |> range(start: -1d)
    |> filter(fn: (r) => r._measurement == "example-measurement")
    |> mean()
    |> yield(name: "_results")

{{% /code-tab-content %}} {{% code-tab-content %}}

import "sql"

sql.from(
    driverName: "postgres",
    dataSourceName: "postgresql://user:password@localhost",
    query: "SELECT * FROM TestTable",
)
    |> filter(fn: (r) => r.UserID == "123ABC456DEF")
    |> mean(column: "purchase_total")
    |> yield(name: "_results")

{{% /code-tab-content %}} {{< /code-tabs-wrapper >}}

Each example includes the following functions (in the order listed):

• from() to retrieve data from the data source.
• Pipe-forward operator (|>) to send the output of each function to the next function as input.
• range(), filter(), or both to filter data based on column values.
• mean() to calculate the average of values returned from the data source.
• yield() to yield results to the user.

For detailed information about basic Flux queries, see Flux query basics.

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