Insert query problem

[sprofis]

when executing an insert query in java it is not updating the table with the new values.
i've noticed that the problem occurs when the tables contain key/keys. it shows that the query was executed successfully but i can't see the new values.
more over when i'm trying to execute 2 insert queries one after another with the same values, i get an sql exception but now the table updates with the new values...
any ideas anybody?


private static void EndOfHire(int S_id, int P_id, float Rank, String Comment)throws Exception {
Connection conn = getConnection();
Statement st = conn.createStatement();
st = conn.createStatement();
String sql = "INSERT INTO tbl_Hire (Sitter_ID, Parent_ID) VALUES ("+S_id+","+P_id+")";
System.out.println(sql);
st.executeUpdate(sql);