[erlang-questions] Conceptual questions on key-value databases for RDBMs users
Thu Nov 4 23:11:39 CET 2010
Hi Joe, All
I'm far from being a database expert too, so feel free to correct me , but
i believe the assumption of storing simple thing is not a general rule and
should not be associated with SQL. For example, postgresql provides more
complex data types and even user defined ones.
On Thu, Nov 4, 2010 at 11:01 PM, Joe Armstrong <> wrote:
> On Tue, Nov 2, 2010 at 9:14 PM, Silas Silva <> wrote:
> > This is a message I sent to the
> > discussion group. I thought it might be interesting to send it
> > erlang-questions, so here we go...
> > Hi all!
> > I have used SQL RDBMSs for some time. I've never used any very advanced
> > feature, but I know enough of it to make database applications.
> > Nowadays, I decided it would be interesting to learn some NoSQL
> > databases concepts. So I decided to pick up some Erlang and Mnesia, its
> > native key-value database. More than scalability itself, the most
> > valuable feature for me is the possibility of replication and
> > synchronization between nodes.
> > But all pros have cons as companion. The lack of a relationship model
> > is difficult for who is used to RDBMSs. So, my question is:
> > * Is there any guide, tutorial, book, whatever, that tries to introduce
> > NoSQL databases to SQL users?
> > * Key-value databases are surprising simple. I know you solve
> > relationship by denormalizing data. What data should be normalized?
> > What shouldn't? How do you update denormalized data?
> I'm no database expert so don't quote me here ...
> As far as I am concerned traditional databases like SQL suffer
> from the fact that the data stored in an individual column is incredible
> simple - I can store an integer/string/... in a column but these are
> incredibly simple data structures. I want to store and retrieve incredibly
> complicated things - how do I store an XML parse tree in a single cell
> of a database? - How do I store a database in a database ...
> In a decent K-V database the value of the key can be *anything* - an
> entire database for example, a compiler, ... no worries
> Then when I analyse my problem I start thinking "I can store and retrieve
> complex object that keys do I need to solve my problem?"
> I'm not thinking in terms of joins and normalizing things - the thought
> is different - so far I haven't met any problems that don't map onto
> It seems to my that SQL provides you with the ability do to complex
> queries on simple things. K-V dbs can do simple queries on complex
> > Sorry for such simple and general questions. Things were simple up to
> > the moment that I realized that it would be easily solved with a JOIN
> > SQL statement. :-)
> > Thank you very much!
> > --
> > Silas Silva
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