Aggregate Functions

Aggregate functions are many-to-one functions. They perform aggregate calculations on a set of values, resulting in a single aggregated result.

All aggregate functions except COUNT(), COUNT_IF() ignore null values and return null when there are no input rows or all values are null. For example, SUM() returns null instead of zero, and AVG() does not include null values in the count.

The aggregate functions supported by IoTDB are as follows:

Function Name	Function Description	Allowed Input Data Types	required attributes	Output Data Types
SUM	Summation.	INT32 INT64 FLOAT DOUBLE	No	DOUBLE
COUNT	Counts the number of data points.	All types	No	INT
AVG	Average.	INT32 INT64 FLOAT DOUBLE	No	DOUBLE
EXTREME	Finds the value with the largest absolute value. Returns a positive value if the maximum absolute value of positive and negative values is equal.	INT32 INT64 FLOAT DOUBLE	No	Consistent with the input data type
MAX_VALUE	Find the maximum value.	INT32 INT64 FLOAT DOUBLE	No	Consistent with the input data type
MIN_VALUE	Find the minimum value.	INT32 INT64 FLOAT DOUBLE	No	Consistent with the input data type
FIRST_VALUE	Find the value with the smallest timestamp.	All data types	No	Consistent with input data type
LAST_VALUE	Find the value with the largest timestamp.	All data types	No	Consistent with input data type
MAX_TIME	Find the maximum timestamp.	All data Types	No	Timestamp
MIN_TIME	Find the minimum timestamp.	All data Types	No	Timestamp
COUNT_IF	Find the number of data points that continuously meet a given condition and the number of data points that meet the condition (represented by keep) meet the specified threshold.	BOOLEAN	[keep >=/>/=/!=/</<=]threshold：The specified threshold or threshold condition, it is equivalent to keep >= threshold if threshold is used alone, type of threshold is INT64 ignoreNull：Optional, default value is true；If the value is true, null values are ignored, it means that if there is a null value in the middle, the value is ignored without interrupting the continuity. If the value is true, null values are not ignored, it means that if there are null values in the middle, continuity will be broken	INT64
TIME_DURATION	Find the difference between the timestamp of the largest non-null value and the timestamp of the smallest non-null value in a column	All data Types	No	INT64
MODE	Find the mode. Note: 1.Having too many different values in the input series risks a memory exception; 2.If all the elements have the same number of occurrences, that is no Mode, return the value with earliest time; 3.If there are many Modes, return the Mode with earliest time.	All data Types	No	Consistent with the input data type

COUNT

example

select count(status) from root.ln.wf01.wt01;

Result:

+-------------------------------+
|count(root.ln.wf01.wt01.status)|
+-------------------------------+
|                          10080|
+-------------------------------+
Total line number = 1
It costs 0.016s

COUNT_IF

Grammar

count_if(predicate, [keep >=/>/=/!=/</<=]threshold[, 'ignoreNull'='true/false'])

predicate: legal expression with BOOLEAN return type

use of threshold and ignoreNull can see above table

Note: count_if is not supported to use with SlidingWindow in group by time now

example

raw data

+-----------------------------+-------------+-------------+
|                         Time|root.db.d1.s1|root.db.d1.s2|
+-----------------------------+-------------+-------------+
|1970-01-01T08:00:00.001+08:00|            0|            0|
|1970-01-01T08:00:00.002+08:00|         null|            0|
|1970-01-01T08:00:00.003+08:00|            0|            0|
|1970-01-01T08:00:00.004+08:00|            0|            0|
|1970-01-01T08:00:00.005+08:00|            1|            0|
|1970-01-01T08:00:00.006+08:00|            1|            0|
|1970-01-01T08:00:00.007+08:00|            1|            0|
|1970-01-01T08:00:00.008+08:00|            0|            0|
|1970-01-01T08:00:00.009+08:00|            0|            0|
|1970-01-01T08:00:00.010+08:00|            0|            0|
+-----------------------------+-------------+-------------+

Not use ignoreNull attribute (Ignore Null)

SQL:

select count_if(s1=0 & s2=0, 3), count_if(s1=1 & s2=0, 3) from root.db.d1

Result:

+--------------------------------------------------+--------------------------------------------------+
|count_if(root.db.d1.s1 = 0 & root.db.d1.s2 = 0, 3)|count_if(root.db.d1.s1 = 1 & root.db.d1.s2 = 0, 3)|
+--------------------------------------------------+--------------------------------------------------+
|                                                 2|                                                 1|
+--------------------------------------------------+--------------------------------------------------

Use ignoreNull attribute

SQL:

select count_if(s1=0 & s2=0, 3, 'ignoreNull'='false'), count_if(s1=1 & s2=0, 3, 'ignoreNull'='false') from root.db.d1

Result:

+------------------------------------------------------------------------+------------------------------------------------------------------------+
|count_if(root.db.d1.s1 = 0 & root.db.d1.s2 = 0, 3, "ignoreNull"="false")|count_if(root.db.d1.s1 = 1 & root.db.d1.s2 = 0, 3, "ignoreNull"="false")|
+------------------------------------------------------------------------+------------------------------------------------------------------------+
|                                                                       1|                                                                       1|
+------------------------------------------------------------------------+------------------------------------------------------------------------+

TIME_DURATION

Grammar

    time_duration(Path)

Example

raw data

+----------+-------------+
|      Time|root.db.d1.s1|
+----------+-------------+
|         1|           70|
|         3|           10|
|         4|          303|
|         6|          110|
|         7|          302|
|         8|          110|
|         9|           60|
|        10|           70|
|1677570934|           30|
+----------+-------------+

Insert sql

"CREATE DATABASE root.db",
"CREATE TIMESERIES root.db.d1.s1 WITH DATATYPE=INT32, ENCODING=PLAIN tags(city=Beijing)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(1, 2, 10, true)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(2, null, 20, true)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(3, 10, 0, null)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(4, 303, 30, true)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(5, null, 20, true)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(6, 110, 20, true)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(7, 302, 20, true)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(8, 110, null, true)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(9, 60, 20, true)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(10,70, 20, null)",
"INSERT INTO root.db.d1(timestamp,s1,s2,s3) values(1677570934, 30, 0, true)",

SQL:

select time_duration(s1) from root.db.d1

Result:

+----------------------------+
|time_duration(root.db.d1.s1)|
+----------------------------+
|                  1677570933|
+----------------------------+

Note: Returns 0 if there is only one data point, or null if the data point is null.