Question

Am I correct in thinking that for a database with n USERS, the following code results in at least n interations with the database?

Statement stmt = con.createStatement();
ResultSet srs = stmt.executeQuery(
    "SELECT FAVOURITE_COLOR FROM USERS");
while (srs.next()) {
        //performSomeAction on srs.getString("FAVOURITE_COLOR");
}

Would it then also be possible to extract the FAVOURITE_COLOR from all users in 1 I/O interaction with the database?
And if so would that posssibly cause an memory overflow in the program if there are too many users?

Answer 1

Your sample code does a single roundtrip to the database.

In a simple implementation, executeQuery will wait for the entire dataset to be retrieved from the database. Then each call to next will move immediately to the next row.