Question

I am trying to sort the result of my query by equality expression like

   ORDER BY (x = y) ASC

But I keep getting unexpected token =. I even tried things like

   ORDER BY COUNT(x = y) ASC

but with no success either: expecting CLOSE, found '='

Is there a way to achieve this with JPQL? Thanks

Answer 1

No, it will not work that way with JPQL. It is not possible, because

1. x=y is not orderable
2. x=y is not part of SELECT clause.

In JPA 2.0 specification this is told with following words:

An orderby_item must be one of the following:

1. A state_field_path_expression that evaluates to an orderable state field 
   of an entity or embeddable class abstract schema type designated in the 
   SELECT clause by one of the following:
     • a general_identification_variable
     • a single_valued_object_path_expression

2. A state_field_path_expression that evaluates to the same state field of 
   the same entity or embeddable abstract schema type as a      
   state_field_path_expression in the SELECT clause

3. A result_variable that refers to an orderable item in the SELECT clause 
   for which the same result_variable has been specified. This may be the 
   result of an aggregate_expression, a scalar_expression, or a 
   state_field_path_expression in the SELECT clause.

What you can try is to use CASE in SELECT clause to construct numeric attribute and use that in ORDER BY.