Source: https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/variable-definition/agg/avg_agg/
Documentation version: v5.3.2

# AvgAgg

An AvgAgg aggregator value variable (`AvgAgg<T>`) maintains the average of all inputs, where `T` represents the data type of the input values. 

## Declaration syntax

diagramsource

 avg_agg_declaration  

````
avg_agg_declaration ::=
'NODE'? 'VALUE' aggregator_value_variable 'AvgAgg' '<' ('INT8'|'INT16'|'INT32'|'INT64'|'FLOAT'|'DOUBLE') '>'

````

For information about the parameters in the declaration syntax, see [Parameters](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/variable-definition/agg/#parameters).

## Initial value

As indicated in the declaration syntax, an initial value must not be specified during declaration.

## Input type and supported operations

The input type must be `T`, which is specified during declaration.

Both [assignment and aggregation](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/set/) operations are supported:

- Assignment operation (`=`): This operation resets the value of the aggregate value variable. For example, `SET @avg_agg = 10` clears the value held by the aggregate value variable `avg_agg` and sets it to 10. At this point, the total is 10, the count is 1, and the average is 10.
- Aggregation operation (`+=`): This operation accumulates the value into the aggregate value variable and recalculates the average value based on all accumulated values. For example, if `avg_agg` already has a value, executing `SET @avg_agg += 10` does not clear the existing value. Instead, it first adds the value `10` to the accumulated sum of `avg_agg` and increases the count. It then automatically updates its average based on all accumulated values.

## Return type

````
AvgAgg<T> -> DOUBLE

````

The return type is always `DOUBLE` regardless of the input type.

## Examples

The following examples are based on the temporary graph `#movie_temporary_graph` created in [CREATE TEMPORARY GRAPH](https://dev-docs.nebula-graph.io/v5.3.2/database-gql-reference/ddl/graph-projection/create/).

### Global AvgAgg aggregator value variables

````
'''
USE #movie_temporary_graph {
  VALUE global_avg AvgAgg<INT>
  SET @global_avg += 3     // Average: 3.0 (Total: 3, Count: 1)
  SET @global_avg += 7     // Average: 5.0 (Total: 10, Count: 2)
  SET @global_avg += 5     // Average: 5.0 (Total: 15, Count: 3)
  LOG_INFO("@global_avg: ",@global_avg)
  SET @global_avg = 0      // avg: 0 (reset to 0)
  LOG_INFO("@global_avg: ",@global_avg)
}
'''

````

Return:

````
Log:
2025-08-21T08:04:55.522902 INFO  - @global_avg: 5
2025-08-21T08:04:55.524437 INFO  - @global_avg: 0

````

### Node-attached AvgAgg aggregator value variables

````
'''
USE #movie_temporary_graph {
  NODE VALUE node_avg AvgAgg<DOUBLE>

  MATCH (a@User WHERE a.id IN [1,3,4])-[w@Watch]->(b@Movie)
  PER PATH {
    // Accumulate user ratings for movies watched and calculate the average
    // Track each user's average rating for movies watched
    SET a.@node_avg += w.rate
  }
  PER NODE (a) {
    LOG_INFO("a.id: ",a.id, " a.@node_avg: ",a.@node_avg)
  }
}
'''

````

Return:

````
Log:
2025-08-21T08:33:36.002357 INFO  - a.id: 4 a.@node_avg: 2.66667
2025-08-21T08:33:36.002357 INFO  - a.id: 3 a.@node_avg: 3.75
2025-08-21T08:33:36.002357 INFO  - a.id: 1 a.@node_avg: 4.77778

````