More models and knowledge

notes/8.md

@@ -16,5 +16,30 @@ Models can be related between themselves to map dependencies.
   - Incremental: also a table, but can only create new records, not update
   - Ephemeral: it's actually NOT materializing. The model can be used by dependents, but it won't be materialized in the DB. It will truly only be a CTE that gets used by other models. Mostly for intermediate states in transformations.
 
+Materializations can be defined at the model level, folder level and project level. This can be modified in the `dbt_project.yml` file, under the `models` key.
+
+To set materialization config at the model level, one must make a jinja tag at the start of the file and call the `config` dbt function. See an example below:
+
+```python
+{{
+    config(
+        materialized = 'incremental',
+        on_schema_change = 'fail'
+    )
+}}
+```
+
+Incremental materializations need to a block that defines the logic to apply in incremental loads (as opposed to the 'normal' logic, that gets apply on first runs). See below an example:
+
+```SQL
+[... rest of query ...]
+WHERE
+    review_text IS NOT NULL
+{% if is_incremental() %}
+    AND review_date > (SELECT MAX(review_date) FROM {{ this }})
+{% endif %}
+```
+
+Bear in mind that how to define the strategy to determine what should be loaded is up to the engineer. Any SQL can be placed within the `if is_incremental()` block. In the example above, we have a date field that easily signals what's the most recent date the table has currently seen.
 
 ##