In terms of connecting to PostgreSQL (and probably most other 'real' databases), I think the connection string should have more (optional) arguments separated by a comma. The ones I use everyday with PostgreSQL are:
driver=org.postgresql.Driver
url="">
user=userxyz
password=thepassword
Of course this is an example from Java. C must have corresponding parameters. (I hope you are not _requiring_ an ODBC setup.) The point being that you cannot connect to a database by just knowing where it is. You usually need a username and password so the database can determine your access permissions. The driver option probably makes more sense for Java or if you are linking (via static library or shared library) to a native PostgreSQL library. But it can be useful if you are using runtime loading.
I'm sorry, I actually came from the APL world and not the APL2 world (although I know what nested arrays are). I do not understand your SQL∆Select and SQL∆Exec lines do. Could you provide a brief explanation?
Thanks!
Blake