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From Ning Zhang <nzh...@facebook.com>
Subject Re: Help with last 30 day unique user query
Date Fri, 15 Oct 2010 07:10:20 GMT
There are some UDFs that convert a string to epoch time and back to a string.  e.g.,

select from_unixtime(unix_timestamp('2010-10-10', 'yyyy-MM-dd') + 60*60*24*30, 'yyyy-MM-dd')
from src limit 1;

 will given you the date which is 30 days later than 2010-10-10.

On Oct 14, 2010, at 11:36 PM, Vijay wrote:

> Hi, I need help with this scenario. We have a table of events which has columns date,
event (not important for this discussion), and user_id. It is obviously easy to find number
of unique users for each day. I also need to find number of unique users in the last 30 days
for each day. This is also quite simple to do for one day. However, I cannot figure out how
to do this for a range of days. Something like this is pretty straightforward in most RDBMS
but with HiveQL has I'm finding this hard. I might be missing something simple though. Any
help is appreciated. Ideally the query should also be as optimized as possible as this table
could be huge.
> 
> Thanks,
> Vijay
> 


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