JPA count distinct multiple expressions

问题

CriteriaBuilder.countDistinct(Expression e)

It takes one expression only. How to count distinct multiple expressions? For example,

Country              Language
-------------------------------

In JPA CriteriaQuery, how to count different pairs of (country, language)?

Thanks,

回答1:

You cannot do that with JPQL. JPQL BNF is very clear

aggregate_expression ::= { AVG | MAX | MIN | SUM } ([DISTINCT] state_field_path_expression) |
    COUNT ([DISTINCT] identification_variable | state_field_path_expression |
    single_valued_object_path_expression)

来源：https://stackoverflow.com/questions/37781683/jpa-count-distinct-multiple-expressions