Re: [boost] Boost.SQL?

Subject: Re: [boost] Boost.SQL?
From: Roland Bock (rbock_at_[hidden])
Date: 2010-09-15 11:55:37

On 09/15/2010 05:11 PM, Dave Abrahams wrote:
> Here's a thread that might be interesting for anyone thinking of
> implementing a DSEL for SQL:
> http://markmail.org/message/rzcdlkquko2htvjp
>    
Thanks. Interesting read :-)

Taking one of the examples you gave in that thread:

// -----------------------------
Entry.objects.filter(
    _.headline.startswith('What'),
    _.pub_date<datetime.now(),
    _.pub_date>=datetime(2005, 1, 1)
);
// -----------------------------

Here's what I want to achieve (and my prototype is very close):

// -----------------------------
[...] where(
             t.headline.startswith("What")
&& t.pub_date < datetime.now(),
&& t.pub_date >= datetime(2005, 1, 1)
);
// -----------------------------

(t being an instance of the table class)

Admittedly, I write "where" instead of "filter", but other than that, 
this is pretty close, right? :-)

> I notice that most of this thread is going in the direction of trying
> to replicate SQL syntax instead of doing something closer to normal
> logic.  I'd be much happier to use a syntax that just specifies "what
> I want" rather than "how to get there."  In some cases the library
> could be responsible for conjuring up JOINs, for example, when that's
> the most efficient approach.
>    

My current code automatically determines which tables you need for your 
query. Thus, the FROM part is not your responsibility. But no other 
magic is conjured up...

Do you have something more specific in mind regarding the syntax? Here 
is an example from http://sqlzoo.net/select_select

SELECT name, A.region
   FROM
      bbc AS A
      JOIN
      (SELECT region,MAX(population) AS maxpop FROM bbc GROUP BY region) 
AS B
   ON (A.region=B.region AND A.population=maxpop)

It selects the names of the population-wise biggest countries from each 
region.

How would you want to express that?

Regards,

Roland