Question

I am trying to write the following SQL query as a JPA query. The SQL query works (MySQL database) but I don’t know how to translate it. I get a error token right after the first FROM. There are probably other errors here too because I was not able to find any guides on how to do sub-queries in the from part, aliasing and so on.

SQL query

SELECT tbl.* from (
  SELECT u.*, COUNT(u.id) AS question_count FROM app_user AS u 
        INNER JOIN question AS q ON u.id = q.user_id GROUP BY u.id  
) AS tbl ORDER BY tbl.question_count DESC LIMIT 10;

JPA query:

SELECT tbl FROM (SELECT u, COUNT(u.id) question_count FROM User u 
INNER JOIN u.questions q ON u.id = q.user_id GROUP BY u.id) tbl 
ORDER BY tbl.question_count LIMIT 10")

Answer 1

I can’t test this with anything right now, but something along the lines of:

final String queryStr = "SELECT u, COUNT(u.id) FROM User u, Questions q WHERE u.id = q.user_id GROUP BY u.id ORDER BY COUNT(u.id) DESC";
Query query = em().createQuery(queryStr);
query.setMaxResults(10);
List<Object[]> results = query.getResultList(); //Index [0] will contain the User-object, [1] will contain Long with result of COUNT(u.id)