Hi Yik San,
`toDataStream` and `toChangelogStream` are the new API's for a smooth 
integration of Table API and DataStream API. You can find the full 
documentation here:
https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/dev/table/data_stream_api/Since `toDataStream` and `toChangelogStream` are relatively new and the 
latter is marked as @Experimental in 1.13. The old methods are still 
kept around for some time. There are also some known issues like 
FLINK-22666 and FLINK-22378 that will be fixed in 1.13.1.
`toAppendStream` or `toRetractStream` will be deprecated in 1.14.
So for now both methods are kind of equally important to get the job 
done. But `toDataStream` and `toChangelogStream` are the stable 
long-term solution in 1.13.1+.
Regards,
Timo
On 24.05.21 14:02, Yik San Chan wrote:
> Hi community,
> 
> Flink 1.13 introduces toDataStream. However, I wonder when do we prefer 
> toDataStream overĀ toAppendStream or toRetractStream?
> 
> Thank you!
> 
> Best,
> Yik San