Select Code to Download

 - (a) $hash{$col1} doesn't exist, or
 - $hash{$col1} exists, and...
...
  - (e) $col2 and $col3 define a range between existing keys, or
  - (f) $col2 and $col3 define a range that encompasses one or more ex
+isting keys,
        with extra margins at one or both edges.

  select * from table where col1 = ? and ( col2 >= ? and col3 <= ? )