toAppendStream doesn‘t support consuming update changes which is produced by node GroupAggregate

Exception in thread "main" org.apache.flink.table.api.TableException: toAppendStream doesn't support consuming update changes which is produced by node GroupAggregate(groupBy=[amount, product, user], select=[amount, product, user])

解决方案:

        tEnv.toAppendStream(result, Row.class).print();
        env.execute();

改成:

        tEnv.toRetractStream(result, Row.class).print();
        env.execute();