Basic DB alias instructions, refs #6, #16

Author: simonw

README.md

@@ -37,7 +37,24 @@ Install this library using `pip`:
 
 ## Usage
 
-Add `"django_sql_dashboard"` to your `INSTALLED_APPS`.
+Add `"django_sql_dashboard"` to your `INSTALLED_APPS` in `settings.py`.
+
+Define a `"dashboard"` database alias in `settings.py`. It should look something like this:
+
+```python
+DATABASES = {
+    "default": {
+        "ENGINE": "django.db.backends.postgresql_psycopg2",
+        "NAME": "mydb",
+    },
+    "dashboard": {
+        "ENGINE": "django.db.backends.postgresql_psycopg2",
+        "NAME": "mydb",
+        "OPTIONS": {"options": "-c default_transaction_read_only=on -c statement_timeout=100"},
+    },
+}
+```
+Even better: create a new PostgreSQL role that is limited to read-only SELECT access to a list of tables, following [these instructions](https://til.simonwillison.net/postgresql/read-only-postgresql-user).
 
 Add the following to your `urls.py`: