Changes between Version 3 and Version 4 of ModelInheritance

Timestamp:

Jan 26, 2006, 6:01:32 PM (18 years ago)

Author:

jkocherhans

Comment:

updated to use option 3 for modeling parent relations in sql

ModelInheritance

@@ -36 +36 @@
 === 1. Modeling parent relations in SQL? ===
 
-  1. Foreign key to parent table named $(parenttable)_id
-  2. Foreign key to parent table named 'parent_id'
-  3. 'id' of parent row equals 'id' of child row
+The general consesus seems to be this:
 
-1. and 2. would take up part of the objects namespace. With 1, you couldn't have attributes named $(parenttable)_id or 'parent_id' respectively.
-
-With option 3, auto-incrementing might be harder, but it makes more sense to have 1 id across the board. I think one would expect {{{Place.objects.get(2)}}} to return the "same" object as {{{Restaurant.objects.get(2)}}}.
-
-Here's an example of option 1:
 {{{
 #!sql
@@ -53 +46 @@
 
 CREATE TABLE "myapp_restaurant" (
-    "id" integer NOT NULL PRIMARY KEY,
-    "place_id" integer NOT NULL REFERENCES "myapp_place" ("id"),
+    /* PRIMARY KEY REFERENCES "myapp_places" ("id") works for postgres, what about others? */
+    "id" integer NOT NULL PRIMARY KEY REFERENCES "myapp_places" ("id"), 
     "description" text NOT NULL
 );
 
 CREATE TABLE "myapp_italianrestaurant" (
-    "id" integer NOT NULL PRIMARY KEY,
-    "restaurant_id" integer NOT NULL REFERENCES "myapp_restaurant" ("id"),
-    "has_decent_gnocci" bool NOT NULL
-);
-}}}
-
-and option 3:
-{{{
-#!sql
-CREATE TABLE "myapp_place" (
-    "id" integer NOT NULL PRIMARY KEY,
-    "name" varchar(50) NOT NULL
-);
-
-CREATE TABLE "myapp_restaurant" (
-    "id" integer NOT NULL PRIMARY KEY, /* Could this reference myapp_place's id too? Doubtful. :( */
-    "description" text NOT NULL
-);
-
-CREATE TABLE "myapp_italianrestaurant" (
-    "id" integer NOT NULL PRIMARY KEY, /* Ditto for referencing myapp_restaurant's id */
+    "id" integer NOT NULL PRIMARY KEY REFERENCES "myapp_restaurant" ("id"),
     "has_decent_gnocci" bool NOT NULL
 );