6.4.5: Aggregation Function of hql Query

Hql can also be used on the selected attributes.Aggregate functions. Hql supports the same clustering function as SQL:

Hql Aggregate functions

AVG	Calculate the average Attribute Value
Count	Count the number of selected objects
Max	Maximum Value of statistical attribute values
Min	Measure the minimum value of a property value.
Sum	Calculates the sum of attribute values.

For example, the following hql statement:

Select count (*) from personselect max (P. Age) from person as P

The Select clause also supportsString Connector,Arithmetic OperatorsAndSQL Functions:

Select P. Name | "" | P. Address from person as P

The Select clause can also be used.DistinctAndAllKeyword. The effect is exactly the same as that in SQL.