Aggregate Functions
About 1 min
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