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From: "Ramkrishna.S.Vasudevan" <ramkrishna.vasudevan@huawei.com>
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Subject: RE: HBase table - distinct values
Date: Thu, 11 Oct 2012 10:22:09 +0530
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Are you planning to use region splits? Can the rowkey have the deptno?

Having dept no in another table, may be having a reverse mapping of deptno
to empno may be helpful too if such queries are frequent.

Regards
Ram
> -----Original Message-----
> From: Anoop Sam John [mailto:anoopsj@huawei.com]
> Sent: Thursday, October 11, 2012 9:32 AM
> To: user@hbase.apache.org
> Cc: hbase-user@hadoop.apache.org
> Subject: RE: HBase table - distinct values
> 
> Hi Ravi
>          If dept_no is a CF:qualifier, to know all the dept numbers
> (distinct or not) you need a full table scan. As Doug said if it is a
> frequent online query don't think MR is a good choice..  If the data in
> your emp table is huge a full table scan also wont be that good I
> feel....  Can you guys think about storing dept number in another
> table?  If you people need query like select <empdetails> from emp
> where dept_no=?  (this query also)  you can think about creating
> secondary index implementation and indexing dept_no... You can use
> index table for above query as well as the 1st one you asked about.  :)
> 
> -Anoop-
> ________________________________________
> From: raviprasad.t@polarisFT.com [raviprasad.t@polarisFT.com]
> Sent: Wednesday, October 10, 2012 7:51 PM
> To: user@hbase.apache.org
> Cc: hbase-user@hadoop.apache.org; user@hbase.apache.org
> Subject: RE: HBase table - distinct values
> 
> Hi,
>   Hbase table name  :- emp
>   Column family :- cf
>     Under the column family cf  we will be having the field name
> deptno
> 
> 
> Regards
> Raviprasad. T
> Mobile :-  91- 9894769541
> 
> 
> -----Anoop Sam John <anoopsj@huawei.com> wrote: -----
> To: "user@hbase.apache.org" <user@hbase.apache.org>, "hbase-
> user@hadoop.apache.org" <hbase-user@hadoop.apache.org>
> From: Anoop Sam John <anoopsj@huawei.com>
> Date: 10/10/2012 06:18PM
> Subject: RE: HBase table - distinct values
> 
> Hi
> Your schema? 'deptno'  is a cf:qualifier?
> 
> -Anoop-
> ________________________________________
> From: raviprasad.t@polarisFT.com [raviprasad.t@polarisFT.com]
> Sent: Wednesday, October 10, 2012 4:29 PM
> To: user@hbase.apache.org; hbase-user@hadoop.apache.org
> Subject: HBase table - distinct values
> 
> Hi all,
>   Is it possible to select distinct value from Hbase table.
> 
> Example :-
>    what is the equivalant code for the below Oracle code  in Hbase  ?
> 
>   Select count (distinct deptno) from emp ;
> 
> Regards
> Raviprasad. T
> 
> 
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