docs(duckdb): add public dataset tutorials

storage/duckdb/README.md

@@ -43,6 +43,13 @@ TPC-H Scale Factor 10 (~11 GB raw data, 86.6M rows total, ~60M in `lineitem`).
 
 Each query also pays a small fixed cost (~40 ms) for client connect and pushdown setup — noticeable on the cheapest queries, negligible on the heavy analytical ones. See [`docs/tpch_sf10_query_benchmark.md`](docs/tpch_sf10_query_benchmark.md) and [`docs/tpch_sf10_ingestion_benchmark.md`](docs/tpch_sf10_ingestion_benchmark.md) for full methodology.
 
+## Tutorials
+
+Step-by-step guides for loading and analyzing open datasets with the DuckDB storage engine:
+
+- [NYC Taxi Trips](docs/tutorials/nyc-taxi-trips.md) — loading Parquet via `run_in_duckdb()`, then cross-engine joins between `ENGINE=DuckDB` and `ENGINE=InnoDB` tables. Follows the ClickHouse taxi tutorial.
+- [OWID CO₂ Emissions](docs/tutorials/owid-co2-emissions.md) — loading a CSV dataset and running aggregations and window functions.
+
 ## How It Works
 
 DuckDB is an in-process analytical database. Its performance rests on three pillars:

storage/duckdb/docs/mariadb-duckdb-incompatibilities.md

@@ -63,6 +63,12 @@ MariaDB function semantics differ from DuckDB in several areas. These are handle
 | `POWER()` | `pow()` | Supported natively |
 | `SUBSTRING()` | `substr()` | Supported natively |
 
+### Not translated by the pushdown layer
+
+| Function | Issue | Workaround |
+|---|---|---|
+| `TIMESTAMPDIFF(unit, dt1, dt2)` | The `unit` keyword is not bindable, so the call reaches DuckDB as an unknown `timestampdiff` function and the query fails. DuckDB's own `date_diff()` takes the unit as a string and is not a drop-in match | Use `UNIX_TIMESTAMP()` arithmetic, e.g. `FLOOR((UNIX_TIMESTAMP(dt2) - UNIX_TIMESTAMP(dt1)) / 600) * 10` for minute buckets |
+
 ### Potentially incompatible (not yet triggered)
 
 | User writes | MariaDB canonical | DuckDB status |