Sorry, I don't think I specified that at the beginning. My original/master table has several fields, four of which are relevant to this hierarchical stuff - id, taxon, parent, parent_id.
The first is a numerical key, from 1 to probably somewhere around 8,000 for mammals, 1 to 10,000 for birds, etc. The field taxon holds the names of taxons (e.g. 'Mammalia', 'Canis-lupus'). The field parent holds the names of each taxon's parent. The field parent_id is just a series of numerals matching each taxonomic level. The value is 1 for Mammalia, 2 for each mammal order, 3 for each family, 4 for genera and 5 for species. It looks something like this: ID | TAXON | PARENT | PARENT_ID 1 | Mammalia | Chordata | 1 2 | Carnivora | Mammalia | 2 3 | Canidae | Carnivora | 3 4 | Canis | Canidae | 4 5 | Canis-lupus | Canis | 5 6 | Canis-latrans | Canis | 5 I wonder if that's what you had in mind with taxonid. Should I just rename parent_id to taxon_id?
