starting nested models: description/adding home_id column

Nested_Models.md

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+# Nesting Models
+
+## Objectives
+
+Currently, we only have two unrelated models: people and locations.  Let's add the functionality so that whenever we have JSON that represents a person, it will contain a `home` property, which is the associated `location` object:
+
+```JSON
+{
+    "id":4,
+    "name":"Bob",
+    "age":25,
+    "home": {
+        "id":2,
+        "street": "123 Fake Street",
+        "city": "Aurora",
+        "state": "NY"
+    }
+}
+```
+
+Also, when we have a location, it will contain an array of people objects:
+
+```JSON
+{
+    "id":2,
+    "street": "123 Fake Street",
+    "city": "Aurora",
+    "state": "NY",
+    "inhabitants":[
+        {
+            "id":4,
+            "name":"Bob",
+            "age":25
+        },        
+        {
+            "id":7,
+            "name":"Sally",
+            "age":74
+        },        
+    ]
+}
+```
+
+This will be a one-to-many relationship
+
+## Add home_id to people
+
+First, go into `psql` and add a `home_id` INT column to the `people` table:
+
+```sql
+ALTER TABLE people ADD COLUMN home_id INT;
+```
+
+Now we can give people homes like so:
+
+```sql
+UPDATE people SET home_id = 2 WHERE id = 4;
+```
+
+The previous code will find the row with an `id` of 4 and set the `home_id` column to 2;