text: -- minmax.test
  -- 
  -- execsql {
  --       SELECT y, coalesce(sum(x),0) FROM
  --         (SELECT null AS x, y+1 AS y FROM t1 UNION SELECT * FROM t1)
  --       GROUP BY y ORDER BY y;
  -- }
  SELECT y, coalesce(sum(x),0) FROM
  (SELECT null AS x, y+1 AS y FROM t1 UNION SELECT * FROM t1)
  GROUP BY y ORDER BY y;