Re: [boost] [database] sql statements

From: Eric Niebler (eric_at_[hidden])
Date: 2006-01-18 17:34:03

Andy Tompkins wrote:
> 
> eg:
> stringstream << select << column("c1") << column("table1", "column2") <<
> from << table("table1").as("t1");
> 
> => "SELECT [c1], [t1].[column2] FROM [table1] AS [t1]"
> 
> I believe that a database library for boost should include something
> like this.

A good idea, but IMO you haven't taken it far enough. First, consider 
the RTL, the relational template library 
(http://sdmg.developerpipeline.com/documents/s=9849/cuj0403vertleyb/), 
which gives you strong type-safety when applying relational operations 
to strongly-typed in-memory data. It uses expression templates.

Next, consider xpressive, which allows you to author regular expressions 
either as expression templates OR as strings. It makes use of a generic 
expression template manipulation framework called proto, which makes it 
fairly straightword to define arbitrary transformations on a statically 
typed expression tree.

Now, putting it all together, I imagine a relational library with a 
dual-interface like xpressive, but for SQL instead of regex. SQL 
statements could be expression templates, which when applied to 
in-memory data, yields strongly-typed results. OR, the exact same 
expression template, when used in a different context, might get 
transformed into the equivalent SQL string for remote (lazy?) execution 
with dynamic typing.

Potentially very powerful.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com