If your joining needs are for offline reporting (e.g. not real time search) then you can join by using MapReduce but they are long running jobs. I am using Hive which gives you SQL, but compiles the SQL to mapreduce jobs. I am running on Tab files, but I read Hive now has HBase input formats, meaning you can join HBase tables. It will not be a fast query though, but will meet long running join needs (e.g. reports etc)
Tim On Fri, Mar 19, 2010 at 5:03 PM, Jonathan Gray <jg...@facebook.com> wrote: > At some point joins may be necessary when denormalization is not possible. > > There is no built-in mechanism to do it. It would be a series of > additional Get calls to the second table you are joining against. This > would be helped significantly with a parallel MultiGet which will hopefully > make it to 0.21. > > JG > > > -----Original Message----- > > From: TuX RaceR [mailto:tuxrace...@gmail.com] > > Sent: Friday, March 19, 2010 8:41 AM > > To: hbase-user@hadoop.apache.org > > Subject: Re: How to join tables in HBase 20.3 > > > > Hi Raffi, > > > > when dealing with key-value stores, you need to think in a different > > way > > see for instance: > > > > http://wiki.apache.org/hadoop/Hbase/DataModel > > > > "Getting high scalability from your relational database isn't done by > > simply adding more machines because its data model is based on a > > single-machine architecture. For example, a JOIN between two tables is > > done in memory and does not take into account the possibility that the > > data has to go over the wire." > > > > JOIN simply does not scale in relational databases. > > > > > > see also > > > > http://wiki.apache.org/hadoop/Hbase/FAQ#A20 > > > > *20 Are there any Schema Design examples?* > > > > > > Hope this helps, > > > > Cheers > > TuX > > > > > > Basmajian, Raffi wrote: > > > I am new to HBase and come from a rdbms background. After looking in > > the > > > sample client code it seems fairly easy to query a single table using > > > Get and Scan, but it's not so obvious how to join data across > > multiple > > > tables. > > > > > > Are there any examples on how to read/join data across multiple > > tables? > > > > > > Thank you > > > > > > Raffi Basmajian > > > > > > > > > --------------------------------------------------------------------- > > --------- > > > This e-mail transmission may contain information that is proprietary, > > privileged and/or confidential and is intended exclusively for the > > person(s) to whom it is addressed. Any use, copying, retention or > > disclosure by any person other than the intended recipient or the > > intended recipient's designees is strictly prohibited. If you are not > > the intended recipient or their designee, please notify the sender > > immediately by return e-mail and delete all copies. OppenheimerFunds > > may, at its sole discretion, monitor, review, retain and/or disclose > > the content of all email communications. > > > > > ======================================================================= > > ======= > > > > > > > >
