public void executeSQL(List<String> data) {
    	try {
			Class.forName("com.mysql.jdbc.Driver").newInstance();
		} catch (InstantiationException | IllegalAccessException | ClassNotFoundException e1) {
			e1.printStackTrace();
		}
		String connectionUrl = "jdbc:mysql://localhost:6000/user_data";
		String connectionUser = "test";
		String connectionPassword = "testtest123";

    	String query = "INSERT INTO user_promocode(user_id, promocode) VALUES(?,?)";
    	Connection conn = null;
    	try {
    		conn = DriverManager.getConnection(connectionUrl, connectionUser, connectionPassword);
    		conn.setAutoCommit(false);
			try (PreparedStatement stmt = conn.prepareStatement(query)) {
				for(String userId : data) {
					stmt.setString(1, userId);
					stmt.setString(2, "PRE10");
					stmt.addBatch();

					stmt.setString(1, userId);
					stmt.setString(2, "POST10");
					stmt.addBatch();
				}
				int[] updateCounts = stmt.executeBatch();
				System.out.println("update counts: " + updateCounts);
			}
    	} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			if(conn != null) {
				try {
					conn.commit();
					conn.setAutoCommit(true);
				} catch (SQLException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
    }