> You're still not getting it. First-class status means that anywhere a value or variable can be used, a query or table should also be able to appear, and vice versa. This means a table or query can appear as a return type, a parameter to a stored procedure or query, a variable, and so on.
I doubt you could implement a query planner that would cope with that degree of flexibility. Which means you’d be forced to deal with the mechanics of the query, pushing you away from declarative SQL and into procedural and functional programming. At which point you might as well ditch SQL anyway.
Without these features, people have to resort to dynamically generated SQL queries in procedural or functional languages, which is much worse! SQL has also become significantly more complicated by adding all sorts of second-class features to get around this composability limitation (CTEs, table valued functions, views, etc.).
Besides, I don't think it would be as bad as you say. You can approach it as a simple template expansion into flat SQL queries except where a data dependency occurs, at which point template expansion proceeds in stages, one for each dependency.
LINQ on .NET provides most of the composability I'm talking about, although it has a few limitations as well. Still worlds better than raw SQL.
I doubt you could implement a query planner that would cope with that degree of flexibility. Which means you’d be forced to deal with the mechanics of the query, pushing you away from declarative SQL and into procedural and functional programming. At which point you might as well ditch SQL anyway.