28 KiB
Window functions let you calculate running totals, moving averages, or other aggregate-like results without collapsing rows into groups. They perform their calculations over a “window” of rows, which you can partition and order in various ways, and return a calculated value for each row in the set.
Unlike non-window aggregate functions that combine each group into a single row, window functions preserve each row’s identity and calculate an additional value for every row in the partition.
For example, the following query uses the {{< influxdb3/home-sample-link >}} and returns each temperature reading with the average temperature per room over the queried time range:
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
avg(temp) OVER (PARTITION BY room) AS avg_room_temp
FROM
home
WHERE
time >= '2022-01-01T08:00:00Z'
AND time <= '2022-01-01T09:00:00Z'
ORDER BY
room,
time
time | room | temp | avg_room_temp |
---|---|---|---|
2022-01-01T08:00:00 | Kitchen | 21.0 | 22.0 |
2022-01-01T09:00:00 | Kitchen | 23.0 | 22.0 |
2022-01-01T08:00:00 | Living Room | 21.1 | 21.25 |
2022-01-01T09:00:00 | Living Room | 21.4 | 21.25 |
{{% /influxdb/custom-timestamps %}}
Window frames
As window functions operate on a row, there is a set of rows in the row's
partition that the window function uses to perform the operation. This set of
rows is called the window frame.
Window frame boundaries can be defined using
RANGE
, ROW
, or GROUPS
frame units, each relative to the current row--for
example:
{{< code-tabs-wrapper >}} {{% code-tabs %}} RANGE ROWS GROUPS {{% /code-tabs %}} {{% code-tab-content %}}
SELECT
time,
temp,
avg(temp) OVER (
ORDER BY time
RANGE INTERVAL '3 hours' PRECEDING
) AS 3h_moving_avg
FROM home
WHERE room = 'Kitchen'
{{% /code-tab-content %}} {{% code-tab-content %}}
SELECT
time,
temp,
avg(temp) OVER (
ROWS 3 PRECEDING
) AS moving_avg
FROM home
WHERE room = 'Kitchen'
{{% /code-tab-content %}} {{% code-tab-content %}}
SELECT
time,
room,
temp,
avg(temp) OVER (
ORDER BY room
GROUPS 1 PRECEDING
) AS moving_avg
FROM home
{{% /code-tab-content %}} {{< /code-tabs-wrapper >}}
For more information about how window frames work, see the frame clause.
If you don't specify window frames, window functions use all rows in the current partition to perform their operation.
function([expr])
OVER(
[PARTITION BY expr[, …]]
[ORDER BY expr [ ASC | DESC ][, …]]
[ frame_clause ]
)
OVER clause
Window functions use an OVER
clause that directly follows the window function's
name and arguments.
The OVER
clause syntactically distinguishes a window
function from a non-window or aggregate function and defines how to group and order rows for the window operation.
PARTITION BY clause
The PARTITION BY
clause in the OVER
clause divides the rows into groups, or
partitions, that share the same values of the PARTITION BY
expressions.
The window function operates on all the rows in the same partition as the
current row.
ORDER BY clause
The ORDER BY
clause inside of the OVER
clause controls the order that the
window function processes rows in each partition.
When a window clause contains an ORDER BY
clause, the window frame boundaries
may be explicit or implicit, limiting a window frame size in both directions
relative to the current row.
[!Note] The
ORDER BY
clause in anOVER
clause determines the processing order for rows in each partition and is separate from theORDER BY
clause of the query.
Frame clause
The frame clause defines window frame boundaries and can be one of the following:
{ RANGE | ROWS | GROUPS } frame_start
{ RANGE | ROWS | GROUPS } BETWEEN frame_start AND frame_end
Frame units
When defining window frames, you can use one of the following frame units:
RANGE
Defines frame boundaries using rows with values for columns specified
in the ORDER BY
clause within a value range relative to
the current row value.
[!Important] When using
RANGE
frame units, you must include anORDER BY
clause with exactly one column.
The offset is the difference between the current row value and surrounding
row values. RANGE
supports the following offset types:
- Numeric (non-negative)
- Numeric string (non-negative)
- Interval
{{< expand-wrapper >}}
{{% expand "See how RANGE
frame units work with numeric offsets" %}}
To use a numeric offset with the RANGE
frame unit, you must sort partitions
by a numeric-type column.
... OVER (
ORDER BY wind_direction
RANGE BETWEEN 45 PRECEDING AND 45 FOLLOWING
)
The window frame includes rows with sort column values between 45 below and 45 above the current row's value:
{{< sql/window-frame-units "range numeric" >}}
{{% /expand %}}
{{% expand "See how RANGE
frame units work with interval offsets" %}}
To use an interval offset with the RANGE
frame unit, you must sort partitions
by time
or a timestamp-type column.
... OVER (
ORDER BY time
RANGE BETWEEN
INTERVAL '3 hours' PRECEDING
AND INTERVAL '1 hour' FOLLOWING
)
The window frame includes rows with timestamps between three hours before and one hour after the current row's timestamp:
{{% influxdb/custom-timestamps %}}
{{< sql/window-frame-units "range interval" >}}
{{% /influxdb/custom-timestamps %}}
{{% /expand %}} {{< /expand-wrapper >}}
ROWS
Defines window frame boundaries using row positions relative to the current row.
The offset is the difference in row position from the current row.
ROWS
supports the following offset types:
- Numeric (non-negative)
- Numeric string (non-negative)
{{< expand-wrapper >}}
{{% expand "See how ROWS
frame units work" %}}
When using the ROWS
frame unit, row positions relative to the current row
determine frame boundaries--for example:
... OVER (
ROWS BETWEEN 2 PRECEDING AND 1 FOLLOWING
)
The window frame includes the two rows before and the one row after the current row:
{{< sql/window-frame-units "rows" >}}
{{% /expand %}} {{< /expand-wrapper >}}
GROUPS
Defines window frame boundaries using row groups.
Rows with the same values for the columns in the ORDER BY
clause
comprise a row group.
[!Important] When using
GROUPS
frame units, include anORDER BY
clause.
The offset is the difference in row group position relative to the current row group.
GROUPS
supports the following offset types:
- Numeric (non-negative)
- Numeric string (non-negative)
{{< expand-wrapper >}}
{{% expand "See how GROUPS
frame units work" %}}
When using the GROUPS
frame unit, unique combinations column values specified
in the ORDER BY
clause determine each row group. For example, if you sort
partitions by country
and city
:
... OVER (
ORDER BY country, city
GROUPS ...
)
The query defines row groups in the following way:
{{< sql/window-frame-units "groups" >}}
You can then use group offsets to determine frame boundaries:
... OVER (
ORDER BY country, city
GROUPS 2 PRECEDING
)
The window function uses all rows in the current row group and the two preceding row groups to perform the operation:
{{< sql/window-frame-units "groups with frame" >}}
{{% /expand %}} {{< /expand-wrapper >}}
Frame boundaries
Frame boundaries (frame_start and frame_end) define the boundaries of each frame that the window function operates on.
- UNBOUNDED PRECEDING
- offset PRECEDING
- CURRENT_ROW](#current-row)
- offset> FOLLOWING
- UNBOUNDED FOLLOWING
UNBOUNDED PRECEDING
Starts at the first row of the partition and ends at the current row.
UNBOUNDED PRECEDING
offset PRECEDING
Starts at offset
frame units before the current row and ends at the current row.
For example, 3 PRECEDING
includes 3 rows before the current row.
<offset> PRECEDING
CURRENT ROW
Both starts and ends at the current row when used as a boundary.
CURRENT ROW
offset FOLLOWING
Starts at the current row and ends at offset
frame units after the current row.
For example, 3 FOLLOWING
includes 3 rows after the current row.
<offset> FOLLOWING
UNBOUNDED FOLLOWING
Starts at the current row and ends at the last row of the partition.
offset FOLLOWING
Use a specified offset of frame units after the current row as a frame boundary.
offset FOLLOWING
UNBOUNDED FOLLOWING
Use the current row to the end of the current partition the frame boundary.
UNBOUNDED FOLLOWING
WINDOW clause
Use the WINDOW
clause to define a reusable alias for a window specification.
This is useful when multiple window functions in your query share the same window definition.
Instead of repeating the same OVER clause for each function, define the window once and reference it by alias--for example:
SELECT
sum(net_gain) OVER w,
avg(net_net) OVER w
FROM
finance
WINDOW w AS ( PARTITION BY ticker ORDER BY time DESC);
Aggregate functions
All aggregate functions can be used as window functions.
Ranking Functions
cume_dist
Returns the cumulative distribution of a value within a group of values.
The returned value is greater than 0 and less than or equal to 1 and represents
the relative rank of the value in the set of values.
The ORDER BY
clause in the OVER
clause is used
to correctly calculate the cumulative distribution of the current row value.
cume_dist()
[!Important] When using
cume_dist
, include anORDER BY
clause in theOVER
clause.
{{< expand-wrapper >}}
{{% expand "View cume_dist
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
cume_dist() OVER (
PARTITION BY room
ORDER BY temp
) AS cume_dist
FROM home
WHERE
time >= '2022-01-01T08:00:00Z'
AND time < '2022-01-01T12:00:00Z'
time | room | temp | cume_dist |
---|---|---|---|
2022-01-01T08:00:00 | Living Room | 21.1 | 0.25 |
2022-01-01T09:00:00 | Living Room | 21.4 | 0.5 |
2022-01-01T10:00:00 | Living Room | 21.8 | 0.75 |
2022-01-01T11:00:00 | Living Room | 22.2 | 1.0 |
2022-01-01T08:00:00 | Kitchen | 21.0 | 0.25 |
2022-01-01T11:00:00 | Kitchen | 22.4 | 0.5 |
2022-01-01T10:00:00 | Kitchen | 22.7 | 0.75 |
2022-01-01T09:00:00 | Kitchen | 23.0 | 1.0 |
{{% /influxdb/custom-timestamps %}}
{{% /expand %}} {{< /expand-wrapper >}}
dense_rank
Returns the rank of the current row in its partition.
Ranking is consecutive; assigns duplicate values the same rank number and the rank sequence continues
with the next distinct value (unlike rank()
).
The ORDER BY
clause in the OVER
clause determines
ranking order.
dense_rank()
{{< expand-wrapper >}}
{{% expand "View dense_rank
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
dense_rank() OVER (
PARTITION BY room
ORDER BY temp
) AS dense_rank
FROM home
WHERE
time >= '2022-01-01T08:00:00Z'
AND time < '2022-01-01T12:00:00Z'
time | room | temp | dense_rank |
---|---|---|---|
2022-01-01T08:00:00 | Kitchen | 21.0 | 1 |
2022-01-01T11:00:00 | Kitchen | 22.4 | 2 |
2022-01-01T10:00:00 | Kitchen | 22.7 | 3 |
2022-01-01T09:00:00 | Kitchen | 23.0 | 4 |
2022-01-01T08:00:00 | Living Room | 21.1 | 1 |
2022-01-01T09:00:00 | Living Room | 21.4 | 2 |
2022-01-01T10:00:00 | Living Room | 21.8 | 3 |
2022-01-01T11:00:00 | Living Room | 22.2 | 4 |
{{% /influxdb/custom-timestamps %}}
{{% /expand %}}
{{% expand "Compare dense_rank
, rank
, and row_number
functions"%}}
Consider a table with duplicate ID values. The following query shows how each ranking function handles duplicate values:
SELECT
id,
rank() OVER(ORDER BY id),
dense_rank() OVER(ORDER BY id),
row_number() OVER(ORDER BY id)
FROM my_table;
ID | rank | dense_rank | row_number |
---|---|---|---|
1 | 1 | 1 | 1 |
1 | 1 | 1 | 2 |
1 | 1 | 1 | 3 |
2 | 4 | 2 | 4 |
Key differences:
rank()
assigns the same rank to equal values but skips ranks for subsequent valuesdense_rank()
assigns the same rank to equal values and uses consecutive ranksrow_number()
assigns unique sequential numbers regardless of value (non-deterministic) {{% /expand %}} {{< /expand-wrapper >}}
ntile
Distributes the rows in an ordered partition into the specified number of groups.
Each group is numbered, starting at one.
For each row, ntile
returns the group number to which the row belongs.
Group numbers range from 1 to the expression
value, dividing the partition as
equally as possible.
The ORDER BY
clause in the OVER
clause determines
ranking order.
ntile(expression)
Arguments
- expression: An integer. The number of groups to split the partition into.
{{< expand-wrapper >}}
{{% expand "View ntile
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
temp,
ntile(4) OVER (
ORDER BY time
) AS ntile
FROM home
WHERE
room = 'Kitchen'
AND time >= '2022-01-01T08:00:00Z'
AND time < '2022-01-01T15:00:00Z'
time | temp | ntile |
---|---|---|
2022-01-01T08:00:00 | 21.0 | 1 |
2022-01-01T09:00:00 | 23.0 | 1 |
2022-01-01T10:00:00 | 22.7 | 2 |
2022-01-01T11:00:00 | 22.4 | 2 |
2022-01-01T12:00:00 | 22.5 | 3 |
2022-01-01T13:00:00 | 22.8 | 3 |
2022-01-01T14:00:00 | 22.8 | 4 |
{{% /influxdb/custom-timestamps %}}
{{% /expand %}} {{< /expand-wrapper >}}
percent_rank
Returns the percentage rank of the current row within its partition.
The returned value is between 0
and 1
, computed as:
(rank - 1) / (total_rows - 1)
The ORDER BY
clause in the OVER
clause determines
the ranking order.
percent_rank()
{{< expand-wrapper >}}
{{% expand "View percent_rank
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
percent_rank() OVER (
PARTITION BY room
ORDER BY temp
) AS percent_rank
FROM home
WHERE
time >= '2022-01-01T08:00:00Z'
AND time < '2022-01-01T11:00:00Z'
time | room | temp | percent_rank |
---|---|---|---|
2022-01-01T08:00:00 | Kitchen | 21.0 | 0.0 |
2022-01-01T10:00:00 | Kitchen | 22.7 | 0.5 |
2022-01-01T09:00:00 | Kitchen | 23.0 | 1.0 |
2022-01-01T08:00:00 | Living Room | 21.1 | 0.0 |
2022-01-01T09:00:00 | Living Room | 21.4 | 0.5 |
2022-01-01T10:00:00 | Living Room | 21.8 | 1.0 |
{{% /influxdb/custom-timestamps %}}
{{% /expand %}} {{< /expand-wrapper >}}
rank
Returns the rank of the current row in its partition.
For duplicate values, rank
assigns them the same rank number, skips subsequent ranks (unlike dense_rank()
),
and then continues ranking with the next distinct value.
The ORDER BY
clause in the OVER
clause determines
ranking order.
rank()
{{< expand-wrapper >}}
{{% expand "View rank
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
rank() OVER (
PARTITION BY room
ORDER BY temp
) AS rank
FROM home
WHERE
time >= '2022-01-01T08:00:00Z'
AND time < '2022-01-01T11:00:00Z'
time | room | temp | rank |
---|---|---|---|
2022-01-01T08:00:00 | Living Room | 21.1 | 1 |
2022-01-01T09:00:00 | Living Room | 21.4 | 2 |
2022-01-01T10:00:00 | Living Room | 21.8 | 3 |
2022-01-01T08:00:00 | Kitchen | 21.0 | 1 |
2022-01-01T10:00:00 | Kitchen | 22.7 | 2 |
2022-01-01T09:00:00 | Kitchen | 23.0 | 3 |
{{% /influxdb/custom-timestamps %}}
{{% /expand %}}
{{% expand "Compare dense_rank
, rank
, and row_number
functions"%}}
Consider a table with duplicate ID values. The following query shows how each ranking function handles duplicate values:
SELECT
id,
rank() OVER(ORDER BY id),
dense_rank() OVER(ORDER BY id),
row_number() OVER(ORDER BY id)
FROM my_table;
ID | rank | dense_rank | row_number |
---|---|---|---|
1 | 1 | 1 | 1 |
1 | 1 | 1 | 2 |
1 | 1 | 1 | 3 |
2 | 4 | 2 | 4 |
Key differences:
rank()
assigns the same rank to equal values but skips ranks for subsequent valuesdense_rank()
assigns the same rank to equal values and uses consecutive ranksrow_number()
assigns unique sequential numbers regardless of value (non-deterministic) {{% /expand %}} {{< /expand-wrapper >}}
row_number
Returns the position of the current row in its partition, counting from 1.
The ORDER BY
clause in the OVER
clause determines
row order.
row_number()
{{< expand-wrapper >}}
{{% expand "View row_number
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
row_number() OVER (
PARTITION BY room
ORDER BY temp
) AS row_number
FROM home
WHERE
time >= '2022-01-01T08:00:00Z'
AND time < '2022-01-01T11:00:00Z'
time | room | temp | row_number |
---|---|---|---|
2022-01-01T08:00:00 | Living Room | 21.1 | 1 |
2022-01-01T09:00:00 | Living Room | 21.4 | 2 |
2022-01-01T10:00:00 | Living Room | 21.8 | 3 |
2022-01-01T08:00:00 | Kitchen | 21.0 | 1 |
2022-01-01T10:00:00 | Kitchen | 22.7 | 2 |
2022-01-01T09:00:00 | Kitchen | 23.0 | 3 |
{{% /influxdb/custom-timestamps %}}
{{% /expand %}}
{{% expand "Compare dense_rank
, rank
, and row_number
functions"%}}
Consider a table with duplicate ID values. The following query shows how each ranking function handles duplicate values:
SELECT
id,
rank() OVER(ORDER BY id),
dense_rank() OVER(ORDER BY id),
row_number() OVER(ORDER BY id)
FROM my_table;
ID | rank | dense_rank | row_number |
---|---|---|---|
1 | 1 | 1 | 1 |
1 | 1 | 1 | 2 |
1 | 1 | 1 | 3 |
2 | 4 | 2 | 4 |
Key differences:
rank()
assigns the same rank to equal values but skips ranks for subsequent valuesdense_rank()
assigns the same rank to equal values and uses consecutive ranksrow_number()
assigns unique sequential numbers regardless of value (non-deterministic) {{% /expand %}} {{< /expand-wrapper >}}
Analytical Functions
first_value
Returns the value from the first row of the window frame.
first_value(expression)
Arguments
- expression: Expression to operate on. Can be a constant, column, or function, and any combination of arithmetic operators.
Related functions
{{< expand-wrapper >}}
{{% expand "View first_value
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
first_value(temp) OVER (
PARTITION BY room
ORDER BY time
) AS first_value
FROM home
WHERE
time >= '2022-01-01T08:00:00Z'
AND time < '2022-01-01T11:00:00Z'
ORDER BY room, time
time | room | temp | first_value |
---|---|---|---|
2022-01-01T08:00:00 | Kitchen | 21.0 | 21.0 |
2022-01-01T09:00:00 | Kitchen | 23.0 | 21.0 |
2022-01-01T10:00:00 | Kitchen | 22.7 | 21.0 |
2022-01-01T08:00:00 | Living Room | 21.1 | 21.1 |
2022-01-01T09:00:00 | Living Room | 21.4 | 21.1 |
2022-01-01T10:00:00 | Living Room | 21.8 | 21.1 |
{{% /influxdb/custom-timestamps %}}
{{% /expand %}} {{< /expand-wrapper >}}
lag
Returns the value from the row that is at the specified offset before the current row in the partition. If the offset row is outside the partition, the function returns the specified default.
lag(expression, offset, default)
Arguments
- expression: Expression to operate on. Can be a constant, column, or function, and any combination of arithmetic or string operators.
- offset: How many rows before the current row to retrieve the value of
expression from. Default is
1
. - default: The default value to return if the offset is in the partition. Must be of the same type as expression.
Related functions
{{< expand-wrapper >}}
{{% expand "View lag
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
lag(temp, 1, 0) OVER (
PARTITION BY room
ORDER BY time
) AS previous_value
FROM home
WHERE
time >= '2022-01-01T08:00:00Z'
AND time < '2022-01-01T11:00:00Z'
ORDER BY room, time
time | room | temp | previous_value |
---|---|---|---|
2022-01-01T08:00:00 | Kitchen | 21.0 | 0.0 |
2022-01-01T09:00:00 | Kitchen | 23.0 | 21.0 |
2022-01-01T10:00:00 | Kitchen | 22.7 | 23.0 |
2022-01-01T08:00:00 | Living Room | 21.1 | 0.0 |
2022-01-01T09:00:00 | Living Room | 21.4 | 21.1 |
2022-01-01T10:00:00 | Living Room | 21.8 | 21.4 |
{{% /influxdb/custom-timestamps %}}
{{% /expand %}} {{< /expand-wrapper >}}
last_value
Returns the value from the last row of the window frame.
last_value(expression)
Arguments
- expression: Expression to operate on. Can be a constant, column, or function, and any combination of arithmetic operators.
Related functions
{{< expand-wrapper >}}
{{% expand "View last_value
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
last_value(temp) OVER (
PARTITION BY room
ORDER BY time
ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING
) AS last_value
FROM home
WHERE
time >= '2022-01-01T08:00:00Z'
AND time < '2022-01-01T11:00:00Z'
ORDER BY room, time
time | room | temp | last_value |
---|---|---|---|
2022-01-01T08:00:00 | Kitchen | 21.0 | 22.7 |
2022-01-01T09:00:00 | Kitchen | 23.0 | 22.7 |
2022-01-01T10:00:00 | Kitchen | 22.7 | 22.7 |
2022-01-01T08:00:00 | Living Room | 21.1 | 21.8 |
2022-01-01T09:00:00 | Living Room | 21.4 | 21.8 |
2022-01-01T10:00:00 | Living Room | 21.8 | 21.8 |
{{% /influxdb/custom-timestamps %}}
{{% /expand %}} {{< /expand-wrapper >}}
lead
Returns the value from the row that is at the specified offset after the current row in the partition. If the offset row is outside the partition, the function returns the specified default.
lead(expression, offset, default)
Arguments
- expression: Expression to operate on. Can be a constant, column, or function, and any combination of arithmetic or string operators.
- offset: How many rows before the current row to retrieve the value of
expression from. Default is
1
. - default: The default value to return if the offset is in the partition. Must be of the same type as expression.
Related functions
{{< expand-wrapper >}}
{{% expand "View lead
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
lead(temp, 1, 0) OVER (
PARTITION BY room
ORDER BY time
) AS next_value
FROM home
WHERE
time >= '2022-01-01T08:00:00Z'
AND time < '2022-01-01T11:00:00Z'
ORDER BY room, time
time | room | temp | next_value |
---|---|---|---|
2022-01-01T08:00:00 | Kitchen | 21.0 | 23.0 |
2022-01-01T09:00:00 | Kitchen | 23.0 | 22.7 |
2022-01-01T10:00:00 | Kitchen | 22.7 | 0.0 |
2022-01-01T08:00:00 | Living Room | 21.1 | 21.4 |
2022-01-01T09:00:00 | Living Room | 21.4 | 21.8 |
2022-01-01T10:00:00 | Living Room | 21.8 | 0.0 |
{{% /influxdb/custom-timestamps %}}
{{% /expand %}} {{< /expand-wrapper >}}
nth_value
Returns the value from the row that is the nth row of the window frame (counting from 1). If the nth row doesn't exist, the function returns null.
nth_value(expression, n)
Arguments
- expression: The expression to operator on. Can be a constant, column, or function, and any combination of arithmetic or string operators.
- n: Specifies the row number in the current frame and partition to reference.
{{< expand-wrapper >}}
{{% expand "View lead
query example" %}}
The following example uses the {{< influxdb3/home-sample-link >}}.
{{% influxdb/custom-timestamps %}}
SELECT
time,
room,
temp,
nth_value(temp, 2) OVER (
PARTITION BY room
) AS "2nd_temp"
FROM home
WHERE
time >= '2025-02-10T08:00:00Z'
AND time < '2025-02-10T11:00:00Z'
time | room | temp | 2nd_temp |
---|---|---|---|
2025-02-10T08:00:00 | Kitchen | 21.0 | 22.7 |
2025-02-10T10:00:00 | Kitchen | 22.7 | 22.7 |
2025-02-10T09:00:00 | Kitchen | 23.0 | 22.7 |
2025-02-10T08:00:00 | Living Room | 21.1 | 21.8 |
2025-02-10T10:00:00 | Living Room | 21.8 | 21.8 |
2025-02-10T09:00:00 | Living Room | 21.4 | 21.8 |
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