I spent 2 hours trying to figure out this nonsense. Here is the problem:
Environment *env = Environment::createEnvironment();
Connection *conn = env->createConnection("username", "password",
connectionString);
string sqlQueryText = "UPDATE myTable SET field4 =:p4, field3 =:p3
WHERE field2 :=p2 AND field1 :=p1";
Statement* updateStatement = conn->createStatement(sqlQueryText);
updateStatement.setInt(1, field1Var);
updateStatement.setString(2, field2Var);
updateStatement.setInt(3, field3Var);
updateStatement.setString(4, field4Var);
updateStatement.executeUpdate(conn);