Why are String Formatted Queries Considered So Magical?

[Owen Jacobson]

On 2010-06-28 00:02:57 -0400, Stephen Hansen said:

> On 6/27/10 8:48 PM, Carl Banks wrote:
>> I don't know the exact details of all of these, but I'm going to opine
>> that at least some of these are easily expressible with a function
>> call API.  Perhaps more naturally than with string queries.  For
>> instance, set operations:
>> 
>> query1 = rdb_query(...)
>> query2 = rdb_query(...)
>> 
>> final_query = rdb_union(query1,query2)
>> 
>> or
>> 
>> final_query = query1&  query2
> 
> But, see, that's not actually what's going on behind the scenes in the 
> database. Unless your "query1" and "query2" objects are opaque 
> pseudo-objects which do not actually represent results -- the query 
> planners do a *lot* of stuff by looking at the whole query and 
> computing just how to go about executing all of the instructions.

I believe that *is* his point: that we can replace the SQL language 
with a "query object model" that lets us specify what we want without 
resorting to string-whacking when our needs are dynamic, without 
changing the rest of the workflow. This is obviously true: each RDBMS 
does something very much like what Carl is proposing, internally. 
However, implementing such an API usefully (never mind comfortably) in 
a cross-language way is... difficult, and an RDBMS that can only be 
used from Python (or even from Python and other Smalltalk-like 
languages) is not terribly useful at all.

-o