2.5 KiB
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| GROUP BY clause | Use the `GROUP BY` clause to group query data by column values. |
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203 |
Use the GROUP BY clause to group data by values.
GROUP BY is an optional clause used to group rows that have the same values for all columns and expressions in the list.
To output an aggregation for each group, include an aggregate or selector function in the SELECT statement.
When GROUP BY appears in a query, the SELECT list can only use columns that appear in the GROUP BY list
or in aggregate expressions.
GROUP BY can use column aliases that are defined in the SELECT clause.
GROUP BY can't use an alias named time.
In a GROUP BY list, time always refers to the measurement time column.
Syntax
SELECT
AGGREGATE_FN(field1),
tag1
FROM measurement
GROUP BY tag1
Examples
Group data by tag values
SELECT
AVG("water_level") AS "avg_water_level",
"location"
FROM "h2o_feet"
GROUP BY "location"
{{< expand-wrapper >}}} {{% expand "View example results" %}}
| avg_water_level | location |
|---|---|
| 5.359142420303919 | coyote_creek |
| 3.530712094245885 | santa_monica |
{{% /expand %}} {{< /expand-wrapper >}}
Group results in 15 minute time intervals by tag:
SELECT
"location",
DATE_BIN(INTERVAL '15 minutes', time, TIMESTAMP '2022-01-01 00:00:00Z') AS _time,
COUNT("water_level") AS count
FROM "h2o_feet"
WHERE
time >= timestamp '2019-09-17T00:00:00Z'
AND time <= timestamp '2019-09-17T01:00:00Z'
GROUP BY
_time,
location
ORDER BY
location,
_time
{{< expand-wrapper >}}} {{% expand "View example results" %}}
The query uses the COUNT() function to count the number of water_level points per 15 minute interval.
Results are then ordered by location and time.
| location | _time | count |
|---|---|---|
| coyote_creek | 2019-09-16T23:45:00Z | 1 |
| coyote_creek | 2019-09-17T00:00:00Z | 2 |
| coyote_creek | 2019-09-17T00:15:00Z | 3 |
| coyote_creek | 2019-09-17T00:30:00Z | 2 |
| coyote_creek | 2019-09-17T00:45:00Z | 3 |
| santa_monica | 2019-09-16T23:45:00Z | 1 |
| santa_monica | 2019-09-17T00:00:00Z | 2 |
| santa_monica | 2019-09-17T00:15:00Z | 3 |
| santa_monica | 2019-09-17T00:30:00Z | 2 |
| santa_monica | 2019-09-17T00:45:00Z | 3 |
{{% /expand %}} {{< /expand-wrapper >}}