Поиск строк с минимальными значениями в группе с помощью Criteria API ⇐ JAVA

[Anonymous]

I am trying to create a filter query using JPA Criteria API that finds all those entities that have a lowest value in their group.
For example given a JPA entity "Student" mapping a Table similar to:



id
name
grade
class




1
John
1
A


2
Jim
2
A


3
James
4
B


4
Jordan
3
B



I would like to filter this down to the students that have the lowest grade in their class, in this case

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John

and

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Jordan

.
In SQL this can be accomplished with a self join like this:

Код: Выделить всё

SELECT *
FROM students s1
inner join(
select class, Min(grade) as grade from students group by class
) s2 on s1.class = s2.class and s1.grade = s2.grade;

However I am unable to find a way to create a similar self join approach using the JPA Criteria API.
I can not just JPQL for this as this predicate would have to be added to a large, existing Criteria Predicate.


Источник: https://stackoverflow.com/questions/781 ... iteria-api