vogievetsky commented on issue #8208: Druid SQL: Fetch latest records from 
streaming ingestion
URL: 
https://github.com/apache/incubator-druid/issues/8208#issuecomment-517483429
 
 
   This is funny we were just talking about a very similar thing in the [Slack 
channel](https://druid.apache.org/community/join-slack) the other week...
   
   You can use
   
   ```sql
   SELECT * FROM wikipedia ORDER BY __time DESC LIMIT 1
   ```
   
   To get the latest ingested record this is the most efficient thing you can 
do.
   
   Your query logically would return all the records for the latest time, if 
that is really what you want to do that could be accomplished like so:
   
   ```sql
   SELECT *
   FROM wikipedia
   WHERE __time IN (
     SELECT __time
     FROM wikipedia
     WHERE "__time" >= CURRENT_TIMESTAMP - INTERVAL '1' DAY
     GROUP BY 1
     ORDER BY 1 DESC
     LIMIT 1
   )
   ```
   
   
![image](https://user-images.githubusercontent.com/177816/62331909-45b0d900-b472-11e9-9927-1b644f182dd1.png)
   
   Your query does did not work because it can not plan the result of an 
aggregate (`MAX(__time)`) into a filter. The query above groups on time in the 
inner query.
   Notice also that I apply a filter to the inner query to not have to scan 
across the entire data set - I am assuming that my latest time will always be 
within the last day.
   

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