public static <T> JPQLQuery<T> selectDistinct(Expression<T> expr) {
        return new JPASubQuery<Void>().select(expr).distinct();
    }
Create a new detached JPQLQuery instance with the given projection

@param expr projection
@param <T>
@return select(distinct expr)
querydsl-jpa/src/main/java/com/querydsl/jpa/JPAExpressions.java