I also happened to start casually working on this problem about a month ago without knowing anyone else was working on a similar solution. Well my lib doesn't need to remain a one-man show. As the internals stabilize I hope that others jump in. All contributions will get credited of course.
For the most part, I like Jean-Louis's solution better than my own, except that I think columns need to support column-constraints i.e. primary key, not null, unique, etc. Also, I'm thinking there will be a need for foreign keys to be defined.
That will come too. Like views. And maybe triggers. Currently my roadmap is : CRUD via direct execution ; prepared statements ; placeholders ; transactions ; dialects (Postgres would be a good candidate because it has a non-standard syntax for escaping quotes in string literals). Along the way I (or someone else) will implement "easy" things like constraints and views. I haven't thought a lot about the syntax of constraints yet. My first thoughts were to put them outside the table definition to avoid long arguments lists, e.g. BOOST_RDB_PRIMARY_KEY(Column) would specialize some template responsible for constarint creation. But your syntax looks very nice. I guess that `(constraint::not_null, constraint::default(false) ' builds a mpl::vector of types describing carrying the extra information ? Matus Chochlik uses _ for defaults in Mirror (btw most of the TABLE.COLUMN machinery is inspired by Matus' work). The COLUMN macro could automatically fish from the constraints namespace : BOOST_RDB_BEGIN_TABLE(person) BOOST_RDB_COLUMN(id, integer, (primary_key)) BOOST_RDB_COLUMN(name, varchar<20>, (not_null)) BOOST_RDB_COLUMN(first_name, varchar<30>, _) BOOST_RDB_COLUMN(age, integer, _) BOOST_RDB_COLUMN(married, boolean, (not_null,default(false))) BOOST_RDB_END_TABLE(person) Also we will need a way of forcing the C++ type to something else than the default (currently nested inside integer, varchar<>, etc). And also the column and table names (in case they conflict with C++ keywords). Food for thought... J-L