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From Göran Krampe <go...@krampe.se>
Subject Re: couchdb Comparison
Date Wed, 07 Oct 2009 14:28:54 GMT
Nicholas Orr wrote:
> On Wed, Oct 7, 2009 at 11:53 PM, Rob Stewart
> <robstewart57@googlemail.com> wrote:
>> <snip>
>> Finally.. the dumbest question of all. I realise that CouchDB is a document
>> based database system. But, what are the tools at a users' peril to
>> manipulate the returned data. e.g. In a typical DBMS, one could: " select *
>> from CarList list where list.colour='blue'  ". Or perhaps a SQL join
>> statement, or perhaps a filter statement similar to the Pig filter command.
>>  So is there functionality within CouchDB for this sort of record
>> manipulation, or do I need to code in some other format to create these
>> sorts of functions?
> 
> You need to create "views" via a Map/Reduce function:
> http://wiki.apache.org/couchdb/Introduction_to_CouchDB_views
> Where an RDBMS like MySQL/Oracle/MSSQL have SQL. CouchDB has
> Map/Reduce to query the data

Using an intermediate library in your language of choice you can get 
queries etc to look rather similar, take a look at this C# example 
program for using Divan:

http://github.com/gokr/Divan/blob/master/samples/Trivial/Program.cs

...funny enough it also uses "Cars" as an example :). Note the LINQ 
integration which actually makes it possible to write:

var fastCars = from c in linqCars where c.HorsePowers >= 175 select c;

(given a view for it)

regards, Göran


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