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

JPAQuery supports only the expressivity of JPQL, so window functions are not supported, but paging should work using

query.from(employee).orderBy(employee.id).limit(1)

In case you need to use window functions and you need employee.name and employee.id out this should work

NumberExpression rowNumber = SQLExpressions.rowNumber()
    .over()
    .partitionBy(employee.name)
    .orderBy(employee.id).as("rowNumber");

query.select(employee.name, employee.id)
    .from(SQLExpressions.select(employee.name, employee.id, rowNumber)
                        .from(employee).as(employee))
    .where(Expressions.numberPath(Long.class, "rowNumber").eq(1L))
    .fetch();