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From raviprasa...@polarisFT.com
Subject RE: HBase table - distinct values
Date Thu, 11 Oct 2012 10:36:46 GMT
Hi Anoop,
 Thanks a lot for your reply,
  Actually our requirment is just to count the distinct  deptno from  emp ( Hbase table),
 We are running various pentaho jobs and we need to test the validity of the results, for
that we need the below query.

We need a query to select distinct deptno  from   emp  Hbase table.

Example :- 
  HBase Table name :-  emp,  column_family :=  cf
   Let us say  deptno is the field in the column family cf

emp
----
deptno
10
20
30
10
10
10

The Result should be 
The  count (distinct deptno)  =  3 

We  need just the query to  know the count of  distinct  deptno .

Thanks
Regards
Raviprasad. T
Mobile :-  91- 9894769541


-----Anoop Sam John <anoopsj@huawei.com> wrote: ----- 
To: "user@hbase.apache.org" <user@hbase.apache.org>
From: Anoop Sam John <anoopsj@huawei.com>
Date: 10/11/2012 09:33AM
Cc: "hbase-user@hadoop.apache.org" <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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any use, any form of reproduction, dissemination, copying, disclosure, modification, distribution
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recipient/s is strictly prohibited.

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This e-Mail may contain proprietary and confidential information and is sent for the intended
recipient(s) only.  If by an addressing or transmission error this mail has been misdirected
to you, you are requested to delete this mail immediately. You are also hereby notified that
any use, any form of reproduction, dissemination, copying, disclosure, modification, distribution
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recipient/s is strictly prohibited.

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