JPQL order by expression子句：ORDER BY（x = y）ASC

Question

我试图通过像

这样的等式表达式对查询结果进行排序

   ORDER BY (x = y) ASC

但我一直得到意外的令牌=。我甚至试过像

这样的东西

   ORDER BY COUNT(x = y) ASC

但也没有成功：expecting CLOSE, found '='

有没有办法用JPQL实现这个目标？感谢

Answer 1

不，它不会像JPQL那样工作。这是不可能的，因为

1. x=y无法订购
2. x=y不是SELECT子句的一部分。

在JPA 2.0规范中，用以下词语告知：

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.

您可以尝试在SELECT子句中使用CASE来构造数字属性并在ORDER BY中使用它。