DuckDBClient.sql (#1097)

* implement sql fenced code from DuckDBClient.sql(…)

following @mbostock’s suggestion #1072 (comment)

* fix typo

---------

Co-authored-by: Mike Bostock <[email protected]>

Author: Fil

docs/lib/duckdb.md

@@ -90,4 +90,18 @@ And `db.queryRow`:
 db.queryRow("SELECT count() AS count FROM gaia")
 ```
 
-See the [DatabaseClient Specification](https://observablehq.com/@observablehq/database-client-specification) for more details.
+See the [DatabaseClient Specification](https://observablehq.com/@observablehq/database-client-specification) for more details on these methods.
+
+Finally, the `DuckDBClient.sql` method takes the same arguments as `DuckDBClient.of` and returns the corresponding `db.sql` tagged template literal. The returned function can be used to redefine the built-in [`sql` tagged template literal](../sql#sql-literals) and thereby change the database used by [SQL code blocks](../sql), allowing you to query dynamically-registered tables (unlike the **sql** front matter option).
+
+```js
+const feed = view(Inputs.select(new Map([["M4.5+", "4.5"], ["M2.5+", "2.5"], ["All", "all"]]), {label: "Earthquake feed"}));
+```
+
+```js echo
+const sql = DuckDBClient.sql({quakes: `https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/${feed}_day.csv`});
+```
+
+```sql echo
+SELECT * FROM quakes ORDER BY updated DESC;
+```

docs/sql.md

@@ -27,6 +27,8 @@ sql:
 
 <div class="tip">For performance and reliability, we recommend using local files rather than loading data from external servers at runtime. If needed, you can use a <a href="./loaders">data loader</a> to take a snapshot of a remote data during build.</div>
 
+You can also register tables via code (say to have sources that are defined dynamically via user input) by defining the `sql` symbol with [DuckDBClient.sql](./lib/duckdb).
+
 ## SQL code blocks
 
 To run SQL queries, create a SQL fenced code block (<code>```sql</code>). For example, to query the first 10 rows from the `gaia` table:
@@ -182,6 +184,6 @@ Plot.plot({
 
 The `sql` tag is available by default in Markdown. You can also import it explicitly as:
 
-```js echo
+```js run=false
 import {sql} from "npm:@observablehq/duckdb";
 ```

src/client/stdlib/duckdb.js

@@ -173,6 +173,10 @@ export class DuckDBClient {
     await Promise.all(Object.entries(sources).map(([name, source]) => insertSource(db, name, source)));
     return new DuckDBClient(db);
   }
+
+  static sql() {
+    return this.of.apply(this, arguments).then((db) => db.sql.bind(db));
+  }
 }
 
 Object.defineProperty(DuckDBClient.prototype, "dialect", {