[[esql-stats-by]]
=== `STATS ... BY`
Use `STATS ... BY` to group rows according to a common value and calculate one
or more aggregated values over the grouped rows.

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

Which returns:

[%header,format=dsv,separator=|]
|===
include::{esql-specs}/docs.csv-spec[tag=stats-result]
|===

If `BY` is omitted, the output table contains exactly one row with the
aggregations applied over the entire dataset:

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

Returning:

[%header,format=dsv,separator=|]
|===
include::{esql-specs}/docs.csv-spec[tag=statsWithoutBy-result]
|===

It's possible to calculate multiple values:

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

It's also possible to group by multiple values (only supported for long and
keyword family fields):

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

The following aggregation functions are supported:

* `AVG`
* `COUNT`
* `COUNT_DISTINCT`
* `MAX`
* `MEDIAN`
* `MEDIAN_ABSOLUTE_DEVIATION`
* `MIN`
* `SUM`