每个组中最大的n组

Question

Is there any way in hibernate to get greatest record from a group. In my table I have three columns(error_id, transaction_id, phone) I want to apply order by clause on transaction_id and then make group on basis of phone and then want to get top record from each group.

Any suggestions for this type or query.... Thanx in Advance.

Answer 1

I got the answer from my search.

String msisdnQueryString = "SELECT DISTINCT table.phone FROM TABLE_NAME table";
Query msisdnQueryObject = session.createQuery(msisdnQueryString);
List msisdnList = msisdnQueryObject.list();

List<Long> transactionList = new ArrayList<Long>();
for(Object object : msisdnList){
    Long msisdn = Long.parseLong(object.toString());
    String transactionQueryString = "SELECT table.transactionId FROM TABLE_NAME table WHERE table.phone = "+msisdn+" ORDER BY table.transactionId DESC";
    Query transactionQueryObject = session.createQuery(transactionQueryString);
    transactionQueryObject.setFirstResult(0);
    transactionQueryObject.setMaxResults(1);
    List transactions =transactionQueryObject.list();
    if(transactions.size() > 0){
    transactionList.add((Long)transactions.get(0));
    }
}

It is a long process but it is working. If any one know better way to get such records then please post your answers.