update source.md

docs/source.md

@@ -38,9 +38,19 @@ FileAttachment("data/presse.parquet.sh")
   );
 ```
 
-This is the file that the other pages load with DuckDB, as a FileAttachment:
+This is the file that the other pages reference in the front matter:
 
-```js echo run=false
-import { DuckDBClient } from "npm:@observablehq/duckdb";
-const db = DuckDBClient.of({ presse: FileAttachment("data/presse.parquet") });
+```yaml
+---
+sql:
+  presse: data/presse.parquet
+---
 ```
+
+and process with [sql](https://observablehq.com/framework/sql) code blocks:
+
+````
+```sql
+SELECT COUNT() FROM presse
+```
+````