QueryDSL Window functions

Question

How can I write a query using window functions and selecting all fields in QueryDSL? In the docs there is an example like this:

query.from(employee)
.list(SQ         


        

Answer 1

As written by @timo Window functions (rank, row_number) are not supported by JPQL (JPA 2.1 version) and hence by JPAQuery (QueryDsl Jpa 4.1.4).

You can however rewrite your query so that is does not use rank over():

select a.* from employees a
where
(
    select count(*) from employees b
    where 
       a.department = b.department and
       a.salary <= b.salary
) <= 10
order by salary DESC

This is supported by JPAQuery, it probably goes like this.

final BooleanBuilder rankFilterBuilder = 
    new BooleanBuilder(employee.department.eq(employee2.department));
rankFilterBuilder.and(employee.salary.loe(employee2.salary));

query.from(employee)
.where(JPAExpressions.selectFrom(employee2)
            .where(rankFilterBuilder)
            .select(employee2.count())
            .loe(10))
.orderBy(employee.salary);