Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Plain View
Hive >> mail # user >> how to do random sampling in hive?


+
zuohua zhang 2012-08-14, 22:18
+
Raihan Jamal 2012-08-14, 22:23
+
Roberto Sanabria 2012-08-14, 22:31
Copy link to this message
-
Re: how to do random sampling in hive?
Hi,

To get more accurate sampling, you need to bucketize your table based on the columns you wish to use in sampling. Also use the TABLESAMPLE clause while getting the required sample size in your queries.

http://hive.apache.org/docs/r0.9.0/language_manual/working_with_bucketed_tables.html

https://cwiki.apache.org/Hive/languagemanual-sampling.html 
Regards
Bejoy KS

Sent from handheld, please excuse typos.

-----Original Message-----
From: Roberto Sanabria <[EMAIL PROTECTED]>
Date: Tue, 14 Aug 2012 15:31:14
To: <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Subject: Re: how to do random sampling in hive?

Try this:

select * from table_name order by rand() limit 5;

Cheers,
R

On Tue, Aug 14, 2012 at 3:23 PM, Raihan Jamal <[EMAIL PROTECTED]> wrote:

> I think you can use here LIMIT-
>
> Limit indicates the number of rows to be returned. The rows returned are
> chosen at random. The following query returns 5 rows from t1 at random.
>
>
>
> SELECT * FROM t1 LIMIT 5
>
> http://karmasphere.com/hive-queries-on-table-data
>
>
>
> *Raihan Jamal*
>
>
>
> On Tue, Aug 14, 2012 at 3:18 PM, zuohua zhang <[EMAIL PROTECTED]> wrote:
>
>> Would like to extract a uniform random sample from a hive table? How
>> should I write the query?
>> Thanks!
>>
>
>