Need Help with Multi-Table Query Involving Parents

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Table gzecoregions (GZER) simply matches animal species with ecoregions. Table gWecoregions (GWER) lists all the ecoregions - AND their parents.

So the following query might display a list of all the ecoregions the wolf is native to:

$area_res = mysql_query("SELECT DISTINCT GWER.ERName FROM gwecoregions as GWER

  INNER JOIN gzecoregions GZER ON GZER.Place = GWER.ERID

  WHERE GZER.Animal = '$Animal'"); 

such as...

Alaska Tundra
Canadian Taiga
Siberian Taiga

But I would like to also display the ecoregions' parents (biomes) and the biomes' parents (realms) as well. I discovered that I couldn't do it using just one table, so I created two separate tables for biomes and realms. But I can't figure out how to join them so that I can display something like this:

NEARCTIC (realm)
TUNDRA (biome)
Alaska Tundra
BOREAL FOREST (biome)
Canadian Taiga
PALEARCTIC (realm)
BOREAL FOREST (biome)
Siberian Taiga

It should be easy, but I'm doing something wrong. The following diagrams illustrate the relevant tables and fields...

TABLE: gwecorealms

RealmID | Realm | RealmParent

R-NA | Nearctic | na

R-NT | Neotropical | na

R-NT | Neotropical | sa

R-PA | Paleotropical | eur

R-PA | Paleotropical | afr



TABLE: gwecobiomes

BiomeID | Biome | BiomeParent

B11-NA | Tundra | R-NA

B11-PA | Tundra | R-PA

B11-AA | Tundra | R-AA

B11-AN | Tundra | R-AN

B12-NA | Desert | R-NA



TABLE: gwecoregions

ERID | ERName | ERParent

R-NA | Nearctic | na

R-NT | Neotropical | na

B11-NA | Tundra | R-NA

B11-PA | Tundra | R-PA

B11-AA | Tundra | R-AA

NA1424 | Alaska Tundra | B11-NA

PA1340 | Siberian Tundra | B11-PA 

Note that EVERY are, including all ecoregions, biomes and realms, is included in table gwecoregions, field ERName. So I display my data from that field.

Gwecoregions also has a field named ERParent, which includes the ID of each region's parent, so everything is listed in a parent-child relationship.

Below is a copy of my original query, followed by the query I used to join all four tables. Both queries work, but they produce the same results - a list of ecoregions only. How can I join them so my script also displays the parents?

Thanks.

$area_res = mysql_query("SELECT DISTINCT GWER.ERName FROM gwecoregions as GWER

   INNER JOIN gzecoregions GZER ON GZER.Place = GWER.ERID

   WHERE GZER.Animal = '$Animal'");



 $area_res = mysql_query("SELECT * FROM gwecoregions GWER

   INNER JOIN gzecoregions GZER ON GZER.Place = GWER.ERID

   INNER JOIN gwecobiomes GWEB ON GWEB.BiomeID = GWER.ERParent

   INNER JOIN gwecorealms GWERM ON GWERM.RealmID = GWEB.BiomeParent

   WHERE GZER.Animal = '$Animal' GROUP BY RealmN, BiomeN, ERN");