SQL working [ was Re: The sorry state of the D stack? ]

[Jacob Carlborg]

On 2012-10-07 10:55, Russel Winder wrote:

> Why only PostgreSQL. Shouldn't it also work with MySQL, Oracle, DB2,
> PervasiveSQL, SQLite3, etc.?
>
>  From the example I assume that this is just a library for managing
> connections and that everything else is just string-based SQL
> statements. Groovy's and Python's lowest level is roughly the same.
> However on top of these are expression languages in Groovy / Python so
> as to remove the reliance on string processing, i.e. use an internal DSL
> to do all the SQL stuff. For Python this is SQLAlchemy, for Groovy it
> will hopefully be GSQL. I am sure Scala and C++ have something similar?

They do.

> So I guess the question is how to ensure this all works with all SQL
> systems and how to put an abstraction layer over this to avoid all the
> error prone string manipulation?

ActiveRecord in Ruby on Rails uses several layers to handle all database 
related functionality. At the highest level there's a DSL which allows 
you to write the SQL queries mostly in Ruby. Another library, ARel, is 
used by ActiveRecord to generate the SQL code from the DSL. ARel handles 
all the differences among all the supported databases. ARel then passes 
the SQL code back to ActiveRecord where a lower layer handles the 
connections to the database and performs the actual query.

Then you have another layer that transforms the response into objects, 
sets up all the relations and so on.

-- 
/Jacob Carlborg