Using a CASE statement in HQL select

Question

Is there any way to do the following in HQL:

SELECT 
    case when flag = true then SUM(col1) else SUM(col2)
FROM 
    myTable

Answer 1

We use hibernate HQL query extensively and I think finally there is a hackish way of doing such a thing :

Assuming we originally had a query of

i2.element.id = :someId

Then decided to expand this to be something like this:

((i.element.id = :someId and i2.element.id=:someId) or (i2.element.id = :someId))

But there was an issue where we want it to only lookup for this based on classType so a case statement:

(case when type(i)=Item then 
((i.element.id = :someId and i2.element.id=:someId) or (i2.element.id = :someId))
else
i.element.id = :someId
end)

Above will not work you could make an easy version of above work by doing:

(case when type(i)=Item then 
i2.element.id
else
i.element.id
end)=:elementId

But this does not actually do what we need it to do, we want it to do exact above query, so knowing you can assign a variable at the end of a case statement in there where bit of HQL:

(
                            (
                                (case when 
                                    type(r)=Item then 
                                        i.element.id 
                                    else 
                                        i.element.id end) = :elementId 
                                and 
                                (case when 
                                    type(r)=Item then 
                                        i2.element.id 
                                    else 
                                        i.element.id end) = :elementId
                            )
                            or 
                            (case when 
                                    type(r)=Item then 
                                        i2.element.id 
                                    else 
                                        i.element.id end) = :elementId 
                            )

I have managed to make the query now work based on case statement, sure it is a lot more long winded but actually does the same as the first instance