But  I  have  not  found  there  is  any  syntax to  specify   time   attribute  field  and  watermark  again  with  pure  sql.  

Fabian Hueske <fhueske@gmail.com> 于 2020年5月5日周二 15:47写道:
Sure, you can write a SQL query with multiple interval joins that preserve event-time attributes and watermarks.
There's no need to feed data back to Kafka just to inject it again to assign new watermarks.

Am Di., 5. Mai 2020 um 01:45 Uhr schrieb lec ssmi <shicheng31604@gmail.com>:
I mean using pure sql statement to make it . Can it be possible?  

Fabian Hueske <fhueske@gmail.com> 于2020年5月4日周一 下午4:04写道:

If the interval join emits the time attributes of both its inputs, you can use either of them as a time attribute in a following operator because the join ensures that the watermark will be aligned with both of them.

Best, Fabian

Am Mo., 4. Mai 2020 um 00:48 Uhr schrieb lec ssmi <shicheng31604@gmail.com>:
Thanks for your replay. 
But as I known, if   the time attribute  will be retained and  the time attribute field  of both streams is selected in the result after joining, who is the final time attribute variable?  

Benchao Li <libenchao@gmail.com> 于2020年4月30日周四 下午8:25写道:
Hi lec,

AFAIK, time attribute will be preserved after time interval join.
Could you share your DDL and SQL queries with us?

lec ssmi <shicheng31604@gmail.com> 于2020年4月30日周四 下午5:48写道:
   I need to join multiple stream tables  using  time interval join.  The problem is that the time attribute will disappear  after the jon , and  pure  sql cannot declare the time attribute field again . So, to make is success,  I need to insert  the last result of join to kafka ,and consume it and join it with another stream table  in another flink job . This seems troublesome.
Any good idea?

Benchao Li
School of Electronics Engineering and Computer Science, Peking University
Email: libenchao@gmail.com; libenchao@pku.edu.cn