[[esql-getting-started]]
== Getting started with {esql} queries
++++
<titleabbrev>Getting started</titleabbrev>
++++

This guide shows how you can use {esql} to query and aggregate your data.

[TIP]
====
This getting started is also available as an https://github.com/elastic/elasticsearch-labs/blob/main/notebooks/esql/esql-getting-started.ipynb[interactive Python notebook] in the `elasticsearch-labs` GitHub repository.
====

[discrete]
[[esql-getting-started-prerequisites]]
=== Prerequisites

To follow along with the queries in this guide, you'll need an {es} deployment with our sample data.

include::{es-ref-dir}/tab-widgets/esql/esql-getting-started-sample-data.asciidoc[tag=own-deployment]

[discrete]
[[esql-getting-started-running-queries]]
=== Run an {esql} query

In {kib}, you can use Console or Discover to run {esql} queries:

include::{es-ref-dir}/tab-widgets/esql/esql-getting-started-widget-discover-console.asciidoc[]

[discrete]
[[esql-getting-started-first-query]]
=== Your first {esql} query

Each {esql} query starts with a <<esql-source-commands,source command>>. A
source command produces a table, typically with data from {es}.

image::images/esql/source-command.svg[A source command producing a table from {es},align="center"]

The <<esql-from>> source command returns a table with documents from a data
stream, index, or alias. Each row in the resulting table represents a document.
This query returns up to 1000 documents from the `sample_data` index:

[source,esql]
----
include::{esql-specs}/docs.csv-spec[tag=gs-from]
----

Each column corresponds to a field, and can be accessed by the name of that
field.

[TIP]
====
{esql} keywords are case-insensitive. The following query is identical to the
previous one:

[source,esql]
----
include::{esql-specs}/docs.csv-spec[tag=gs-from-lowercase]
----
====

[discrete]
[[esql-getting-started-limit]]
=== Processing commands

A source command can be followed by one or more
<<esql-processing-commands,processing commands>>, separated by a pipe character:
`|`. Processing commands change an input table by adding, removing, or changing
rows and columns. Processing commands can perform filtering, projection,
aggregation, and more.

image::images/esql/esql-limit.png[A processing command changing an input table,align="center",width="60%"]

For example, you can use the <<esql-limit>> command to limit the number of rows
that are returned, up to a maximum of 10,000 rows:

[source,esql]
----
include::{esql-specs}/docs.csv-spec[tag=gs-limit]
----

[TIP]
====
For readability, you can put each command on a separate line. However, you don't
have to. The following query is identical to the previous one:

[source,esql]
----
include::{esql-specs}/docs.csv-spec[tag=gs-limit-one-line]
----
====

[discrete]
[[esql-getting-started-sort]]
==== Sort a table

image::images/esql/esql-sort.png[A processing command sorting an input table,align="center",width="60%"]

Another processing command is the <<esql-sort>> command. By default, the rows
returned by `FROM` don't have a defined sort order. Use the `SORT` command to
sort rows on one or more columns:

[source,esql]
----
include::{esql-specs}/docs.csv-spec[tag=gs-sort]
----

[discrete]
[[esql-getting-started-where]]
==== Query the data

Use the <<esql-where>> command to query the data. For example, to find all
events with a duration longer than 5ms:

[source,esql]
----
include::{esql-specs}/where.csv-spec[tag=gs-where]
----

`WHERE` supports several <<esql-operators,operators>>. For example, you can use <<esql-like-operator>> to run a wildcard query against the `message` column:

[source,esql]
----
include::{esql-specs}/where-like.csv-spec[tag=gs-like]
----

[discrete]
[[esql-getting-started-more-commands]]
==== More processing commands

There are many other processing commands, like <<esql-keep>> and <<esql-drop>>
to keep or drop columns, <<esql-enrich>> to enrich a table with data from
indices in {es}, and <<esql-dissect>> and <<esql-grok>> to process data. Refer
to <<esql-processing-commands>> for an overview of all processing commands.

[discrete]
[[esql-getting-started-chaining]]
=== Chain processing commands

You can chain processing commands, separated by a pipe character: `|`. Each
processing command works on the output table of the previous command. The result
of a query is the table produced by the final processing command.

image::images/esql/esql-sort-limit.png[Processing commands can be chained,align="center"]

The following example first sorts the table on `@timestamp`, and next limits the
result set to 3 rows:

[source,esql]
----
include::{esql-specs}/docs.csv-spec[tag=gs-chaining]
----

NOTE: The order of processing commands is important. First limiting the result
set to 3 rows before sorting those 3 rows would most likely return a result that
is different than this example, where the sorting comes before the limit.

[discrete]
[[esql-getting-started-eval]]
=== Compute values

Use the <<esql-eval>> command to append columns to a table, with calculated
values. For example, the following query appends a `duration_ms` column. The
values in the column are computed by dividing `event_duration` by 1,000,000. In
other words: `event_duration` converted from nanoseconds to milliseconds.

[source,esql]
----
include::{esql-specs}/eval.csv-spec[tag=gs-eval]
----

`EVAL` supports several <<esql-functions,functions>>. For example, to round a
number to the closest number with the specified number of digits, use the
<<esql-round>> function:

[source,esql]
----
include::{esql-specs}/eval.csv-spec[tag=gs-round]
----

[discrete]
[[esql-getting-started-stats]]
=== Calculate statistics

{esql} can not only be used to query your data, you can also use it to aggregate
your data. Use the <<esql-stats-by>> command to calculate statistics. For
example, the median duration:

[source,esql]
----
include::{esql-specs}/stats.csv-spec[tag=gs-stats]
----

You can calculate multiple stats with one command:

[source,esql]
----
include::{esql-specs}/stats.csv-spec[tag=gs-two-stats]
----

Use `BY` to group calculated stats by one or more columns. For example, to
calculate the median duration per client IP:

[source,esql]
----
include::{esql-specs}/stats.csv-spec[tag=gs-stats-by]
----

[discrete]
[[esql-getting-started-access-columns]]
=== Access columns

You can access columns by their name. If a name contains special characters,
<<esql-identifiers,it needs to be quoted>> with backticks (+{backtick}+).

Assigning an explicit name to a column created by `EVAL` or `STATS` is optional.
If you don't provide a name, the new column name is equal to the function
expression. For example:

[source,esql]
----
include::{esql-specs}/eval.csv-spec[tag=gs-eval-no-column-name]
----

In this query, `EVAL` adds a new column named `event_duration/1000000.0`.
Because its name contains special characters, to access this column, quote it
with backticks:

[source,esql]
----
include::{esql-specs}/eval.csv-spec[tag=gs-eval-stats-backticks]
----

[discrete]
[[esql-getting-started-histogram]]
=== Create a histogram

To track statistics over time, {esql} enables you to create histograms using the
<<esql-bucket>> function. `BUCKET` creates human-friendly bucket sizes
and returns a value for each row that corresponds to the resulting bucket the
row falls into.

Combine `BUCKET` with <<esql-stats-by>> to create a histogram. For example,
to count the number of events per hour:

[source,esql]
----
include::{esql-specs}/bucket.csv-spec[tag=gs-bucket-stats-by]
----

Or the median duration per hour:

[source,esql]
----
include::{esql-specs}/bucket.csv-spec[tag=gs-bucket-stats-by-median]
----

[discrete]
[[esql-getting-started-enrich]]
=== Enrich data

{esql} enables you to <<esql-enrich-data,enrich>> a table with data from indices
in {es}, using the <<esql-enrich>> command.

image::images/esql/esql-enrich.png[align="center"]

Before you can use `ENRICH`, you first need to
<<esql-create-enrich-policy,create>> and <<esql-execute-enrich-policy,execute>>
an <<esql-enrich-policy,enrich policy>>.

include::{es-ref-dir}/tab-widgets/esql/esql-getting-started-enrich-policy.asciidoc[tag=own-deployment]


After creating and executing a policy, you can use it with the `ENRICH`
command:

[source,esql]
----
include::{esql-specs}/enrich.csv-spec[tag=gs-enrich]
----

You can use the new `env` column that's added by the `ENRICH` command in
subsequent commands. For example, to calculate the median duration per
environment:

[source,esql]
----
include::{esql-specs}/enrich.csv-spec[tag=gs-enrich-stats-by]
----

For more about data enrichment with {esql}, refer to <<esql-enrich-data>>.

[discrete]
[[esql-getting-started-process-data]]
=== Process data

Your data may contain unstructured strings that you want to
<<esql-process-data-with-dissect-and-grok,structure>> to make it easier to
analyze the data. For example, the sample data contains log messages like:

[source,txt]
----
"Connected to 10.1.0.3"
----

By extracting the IP address from these messages, you can determine which IP has
accepted the most client connections.

To structure unstructured strings at query time, you can use the {esql}
<<esql-dissect>> and <<esql-grok>> commands. `DISSECT` works by breaking up a
string using a delimiter-based pattern. `GROK` works similarly, but uses regular
expressions. This makes `GROK` more powerful, but generally also slower.

In this case, no regular expressions are needed, as the `message` is
straightforward: "Connected to ", followed by the server IP. To match this
string, you can use the following `DISSECT` command:

[source,esql]
----
include::{esql-specs}/dissect.csv-spec[tag=gs-dissect]
----

This adds a `server_ip` column to those rows that have a `message` that matches
this pattern. For other rows, the value of `server_ip` is `null`.

You can use the new `server_ip` column that's added by the `DISSECT` command in
subsequent commands. For example, to determine how many connections each server
has accepted:

[source,esql]
----
include::{esql-specs}/dissect.csv-spec[tag=gs-dissect-stats-by]
----

For more about data processing with {esql}, refer to
<<esql-process-data-with-dissect-and-grok>>.

[discrete]
[[esql-getting-learn-more]]
=== Learn more

To learn more about {esql}, refer to <<esql-language>> and <<esql-using>>.
