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From torque-...@db.apache.org
Subject [DB Torque Wiki] Updated: FrequentlyAskedQuestions
Date Wed, 05 May 2004 16:03:30 GMT
   Date: 2004-05-05T09:03:30
   Editor: 194.175.229.106 <>
   Wiki: DB Torque Wiki
   Page: FrequentlyAskedQuestions
   URL: http://wiki.apache.org/db-torque/FrequentlyAskedQuestions

   no comment

Change Log:

------------------------------------------------------------------------------
@@ -247,3 +247,26 @@
 While coding your own transactions, make sure that the Database connection is released at
the end. This is ensured in the above code because either Transaction.commit() or Transaction.rollback()
are called, both of which release the database connection. Note that Transaction.safeRollback()
does not release the database connection, so replacing Transaction.rollback() by transaction.safeRollback()
in the above code would lead to the leakage of database connections if the transaction fails.
 
 -- Thomas Fischer
+
+== How can I count datasets in a table ? ==
+
+Suppose one wants to execute a SQL-statement like "select count(*) from employee where name='james'".

+
+'''Answer:''' This query can be executed using the following code (assuming the employee
Table has at least two Columns: "NAME" and "ID", where ID is the primary key, and the Peer
class to the employee Table is EmployeePeer (sorry the link does not work but I don't know
how to get rid of it)):
+{{{
+int numberOfRecords;
+{
+  org.apache.torque.util.Criteria criteria = new org.apache.torque.util.Criteria();
+  criteria.add(EmployeePeer.NAME, "james");
+  criteria.addSelectColumn("COUNT(" + EmployeePeer.ID + ")");
+  java.util.List result = EmployeePeer.doSelectVillageRecords(criteria);
+  com.workingdogs.village.Record record = (com.workingdogs.village.Record) result.get(0);
+  numberOfRecords = record.getValue(1).asInt();
+}
+}}}
+
+I don't know which columns should be used in addSelectColumn (and if it makes a difference
which one is used), but I presume using the primary key is fine. Note that addSelectColumn("count(*)")
does not work.
+
+The answer was put together from articles by Scott Eade and Tulsi Das on the Torque Users
Mailing List.
+
+-- Thomas Fischer

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