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From Anoop Sam John <anoo...@huawei.com>
Subject RE: HBase table - distinct values
Date Thu, 11 Oct 2012 04:01:58 GMT
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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