Aggregate Function

Aggregate Functions are primarily used to group current data and perform aggregation operations on elements within each group, ultimately producing only a single value for each group. The Aggregate Functions supported by NeuG are as follows:

Function	Description	Can be used with DISTINCT	Example
count	return the row counts	YES	RETURN count(a.name);
collect	collect the elements in a single list	YES	RETURN collect(a.name);
min	return the minimum value	NO	RETURN min(a.age);
max	return the maximum value	NO	RETURN max(a.age);
sum	sum up the value	NO	RETURN sum(a.age);
avg	return the average value	NO	RETURN avg(a.age);

NULL Value Handling

When the input is empty, count() and sum return 0, collect returns [], and avg, min, and max return NULL.
When the input contains NULL values, all aggregate functions ignore them. In particular, count(*) counts every input row, including rows containing NULL values.
When the input consists entirely of NULL values, the aggregate results after ignoring NULL are the same as for empty input: count() and sum return 0, collect returns [], and avg, min, and max return NULL. count(*) still returns the total number of input rows.

Input	`count(expr)`	`count(*)`	`collect`	`min`	`max`	`sum`	`avg`
`[]`	`0`	`0`	`[]`	`NULL`	`NULL`	`0`	`NULL`
`[1, NULL, 2]`	`2`	`3`	`[1, 2]`	`1`	`2`	`3`	`1.5`
`[NULL, NULL]`	`0`	`2`	`[]`	`NULL`	`NULL`	`0`	`NULL`