java jdbc accessing multiple resultsets

Question

I have the following structure:

List -->List_Participant -->Participant

so a list may contain several participants.I try to read this in java:

Answer 1

You can try using two different Statement instances for each query. See the JavaDoc for java.sql.Statement. The following example shows the principle.

    Statement statement1 = connection.createStatement();
    Statement statement2 = connection.createStatement();

    ResultSet resultSet1 = statement1.executeQuery("select * from list");
    while(resultSet1.next()){
        String name = resultSet1.getString("Name");

        ResultSet resultSet2 = statement2.executeQuery("select * from List_Participant where name= '"+name+"'");
        while(resultSet2.next()){
            // get the participants
        }
    }

BUT: This is not standard usage of JDBC or SQL for good reasons. It deprives the database of any optimization possibility and moves to much data between the DB and your app for no good reason (See the comments of JohnSkeet and BalusC).

Better use appropriate JOINsin your one and only statement. This can be optimized by the DB:

SELECT lp.* FROM list l JOIN List_Participant lp ON l.name = lp.name

Add any filters/conditions you like to minimize the data retrieved.