SQL repr in zsdatab API

zsdatab_01.cxx

#include <zsdatable.hpp>
#include <iostream>

int main() {
  zsdatab::metadata mt(':');
  mt += { "k", "w", "v" };
  zsdatab::table tab(mt);

  // insert something into table
  ///...
  ///...

  const auto sp_k = ???; // ? = k
  const auto sp_w = ???; // ? < w
  
  const auto fi_w = mt.get_field_nr("w");
  const auto fi_v = mt.get_field_nr("v");

  zsdatab::table result(zsdatab::metadata(mt.separator()) += { "w", "v" });

  // break after 1 iteration
  for(auto &&i : tab.filter("k", sp_k).sort().data()) {
    if(i[fi_w] > sp_w)
      result += { i[fi_w], i[fi_v] };
    break;
  }
  
  if(!result.empty())
    cout << result.get_metadata().serialize(result.data().front());
}

zz_01.sql

CREATE TABLE t(k, w, v);
CREATE INDEX i ON t(k ASC, w ASC);
-- insert something into the table
SELECT w, v FROM t WHERE ? = k AND ? < w ORDER BY w LIMIT 1;