-
Language:
English
-
Language:
English
Red Hat Training
A Red Hat training course is available for JBoss Enterprise Application Platform Common Criteria Certification
14.6. The select clause
The
select
clause picks which objects and properties to return in the query result set. Consider the following:
select mate from Cat as cat inner join cat.mate as mate
The query will select
mate
s of other Cat
s. You can express this query more compactly as:
select cat.mate from Cat cat
Queries can return properties of any value type including properties of component type:
select cat.name from DomesticCat cat where cat.name like 'fri%'
select cust.name.firstName from Customer as cust
Queries can return multiple objects and/or properties as an array of type
Object[]
:
select mother, offspr, mate.name from DomesticCat as mother inner join mother.mate as mate left outer join mother.kittens as offspr
Or as a
List
:
select new list(mother, offspr, mate.name) from DomesticCat as mother inner join mother.mate as mate left outer join mother.kittens as offspr
Or - assuming that the class
Family
has an appropriate constructor - as an actual typesafe Java object:
select new Family(mother, mate, offspr) from DomesticCat as mother join mother.mate as mate left join mother.kittens as offspr
You can assign aliases to selected expressions using
as
:
select max(bodyWeight) as max, min(bodyWeight) as min, count(*) as n from Cat cat
This is most useful when used together with
select new map
:
select new map( max(bodyWeight) as max, min(bodyWeight) as min, count(*) as n ) from Cat cat
This query returns a
Map
from aliases to selected values.