How can you merge several IoT datasets

Hi,

Our IoT devices are sending 9 update MQTT messages every 15 minutes interval (one for each parameter). We did not use the "document" topic as there will most likely duplication of data that lead to inaccuracy. So we are leaning toward following design:

IoT devices -----(9 MQTT/15 minutes, each one would have slight variation in timestamp)------> IoT Core (9 rules) ---------> 9 IoT channels -> 9 pipelines -> 9 datastore -> 9 datasets.

The problem now is that we need a way to merge the 9 datasets together.

Looking for any suggestion on merging and potential designs to work around this.

Thanks,
Steven