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() 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	Output Data Types
SUM	Summation.	INT32 INT64 FLOAT DOUBLE	DOUBLE
COUNT	Counts the number of data points.	All types	INT
AVG	Average.	INT32 INT64 FLOAT DOUBLE	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	Consistent with the input data type
MAX_VALUE	Find the maximum value.	INT32 INT64 FLOAT DOUBLE	Consistent with the input data type
MIN_VALUE	Find the minimum value.	INT32 INT64 FLOAT DOUBLE	Consistent with the input data type
FIRST_VALUE	Find the value with the smallest timestamp.	All data types	Consistent with input data type
LAST_VALUE	Find the value with the largest timestamp.	All data types	Consistent with input data type
MAX_TIME	Find the maximum timestamp.	All data Types	Timestamp
MIN_TIME	Find the minimum timestamp.	All data Types	Timestamp

Example: Count Points

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

Result:

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