Feature / SQL: Reasonably finish page by ...

- providing a canonical powerful SQL example
- guiding the reader to the "Advanced Querying" and "All Features" pages

Author: amotl

docs/feature/sql/index.md

@@ -4,6 +4,8 @@
 
 :::{include} /_include/links.md
 :::
+:::{include} /_include/styles.html
+:::
 
 :::::{grid}
 :padding: 0
@@ -72,10 +74,36 @@ off-the-shelve, 3rd-party, open-source, and proprietary applications.
 
 ## Synopsis
 
-:::{todo}
-- One or max. two DQL SQL queries using many features, all at once?
-- What else?
-:::
+Use scalar functions, sub-selects, and windowing, specifically illustrating the
+DATE_BIN function for resampling time series data using DATE_BIN, also known as
+grouping rows into time buckets, aka. time bucketing.
+
+```sql
+SELECT
+  ts_bin,
+  battery_level,
+  battery_status,
+  battery_temperature
+FROM (
+  SELECT
+  DATE_BIN('5 minutes'::INTERVAL, "time", 0) AS ts_bin,
+  battery_level,
+  battery_status,
+  battery_temperature,
+  ROW_NUMBER() OVER (PARTITION 
+    BY DATE_BIN('5 minutes'::INTERVAL, "time", 0)
+    ORDER BY "time" DESC) AS "row_number"
+  FROM doc.sensor_readings
+) x
+WHERE "row_number" = 1
+ORDER BY 1 ASC
+```
+
+
+## Learn
+
+Please inspect more advanced SQL capabilities on the [](#query) page,
+and read about [](#features) in general.
 
 
 
@@ -87,7 +115,3 @@ off-the-shelve, 3rd-party, open-source, and proprietary applications.
 [](#timeseries) •
 [](#machine-learning)
 :::
-
-
-```{include} /_include/styles.html
-```