docs-v2/content/influxdb/cloud-dedicated/reference/influxql/subqueries.md

title	description	menu	weight	list_code_example
InfluxQL subqueries	An InfluxQL subquery is a query nested in the `FROM` clause of an InfluxQL query. The outer query queries results returned by the inner query (subquery).	influxdb_cloud_dedicated name identifier parent Subqueries influxql-subqueries influxql-reference	207	```sql SELECT_clause FROM ( SELECT_statement ) [...] ```

An InfluxQL subquery is a query nested in the FROM clause of an InfluxQL query. The outer query queries results returned by the inner query (subquery).

• Syntax
• Examples
• Notable subquery behaviors

{{% note %}} InfluxQL does not support a HAVING clause, however InfluxQL subqueries offer functionality similar to the SQL HAVING clause. {{% /note %}}

Syntax

SELECT_clause FROM ( SELECT_statement ) [...]

When using subqueries, InfluxQL performs the inner query first, then performs the outer query.

The outer query requires a SELECT clause and a FROM clause. The inner query is enclosed in parentheses in the outer query's FROM clause.

InfluxQL supports multiple nested subqueries:

SELECT_clause FROM ( SELECT_clause FROM ( SELECT_statement ) [...] ) [...]

Examples

{{% note %}}

Sample data

The examples below use the following sample data sets:

• Get started home sensor data
• Random numbers sample data {{% /note %}}

{{< expand-wrapper >}}

{{% expand "Apply an aggregate function to an aggregated result set" %}}

SELECT
  SUM(max)
FROM
  (
    SELECT
      MAX(temp)
    FROM
      home
    GROUP BY
      room
  )

{{% influxql/table-meta %}} Table: home {{% /influxql/table-meta %}}

time	sum
1970-01-01T00:00:00Z	46.1

{{% /expand %}}

{{% expand "Calculate the average difference between two fields" %}}

SELECT
  MEAN(difference)
FROM
  (
    SELECT
      a - b AS difference
    FROM
      numbers
  )

{{% influxql/table-meta %}} Table: numbers {{% /influxql/table-meta %}}

time	mean
1970-01-01T00:00:00Z	-0.03629771779732732

{{% /expand %}}

{{% expand "Filter aggregate values based on a threshold" %}} {{% influxdb/custom-timestamps %}}

SELECT
  co_change
FROM
  (
    SELECT
      SPREAD(co) AS co_change
    FROM
      home
    GROUP BY
      room,
      time(2h)
  )
WHERE
  time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T20:00:00Z'
  AND co_change >= 4

{{% influxql/table-meta %}} Table: home {{% /influxql/table-meta %}}

time	co_chnage
2022-01-01T18:00:00Z	4
2022-01-01T18:00:00Z	5

{{% /influxdb/custom-timestamps %}} {{% /expand %}}

{{% expand "Perform additional aggregate operations on aggregate values" %}} {{% influxdb/custom-timestamps %}}

SELECT
  SUM(co_derivative) AS sum_derivative
FROM
  (
    SELECT
      DERIVATIVE(MEAN(co)) AS co_derivative
    FROM
      home
    GROUP BY
      time(12m),
      room
  )
WHERE
  time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T20:00:00Z'
GROUP BY
  room

{{% /influxdb/custom-timestamps %}}

{{% influxql/table-meta %}} Table: home {{% /influxql/table-meta %}}

time	room	sum_derivative
1970-01-01T00:00:00Z	Kitchen	5.2
1970-01-01T00:00:00Z	Living Room	3.4

{{% /expand %}} {{< /expand-wrapper >}}

Notable subquery behaviors

• Apply time bounds to the outer query to improve performance
• Cannot use multiple SELECT statements in a subquery

Apply time bounds to the outer query to improve performance

To improve the performance of InfluxQL queries that use subqueries and a specified time range, apply the WHERE clause with time-based predicates to the outer query rather than the inner query. For example--the following queries return the same results, but the query with time-based predicate on the outer query is more performant than the query with time-based predicate on the inner query:

{{% influxdb/custom-timestamps %}}

Time bounds on the outer query

SELECT
  inner_value AS value
FROM
  (
    SELECT
      raw_value as inner_value
  )
WHERE
  time >= '2022-01-01T08:00:00Z'
  AND time <= '2022-01-01T20:00:00Z'

Time bounds on the inner query

SELECT
  inner_value AS value
FROM
  (
    SELECT
      raw_value as inner_value
    WHERE
      time >= '2022-07-19T08:00:00Z'
      AND time <= '2022-01-01T20:00:00Z'
  )

{{% /influxdb/custom-timestamps %}}

Cannot use multiple SELECT statements in a subquery

InfluxQL does not support multiple SELECT statements per subquery:

SELECT_clause FROM (SELECT_statement; SELECT_statement) [...]

However, InfluxQL does support multiple nested subqueries per outer query:

SELECT_clause FROM ( SELECT_clause FROM ( SELECT_statement ) [...] ) [...]
                     ------------------   ----------------
                         Subquery 1          Subquery 2