duckdb

DuckDB v1.5 Skill

DuckDB v1.5.0 "Variegata" — Released 2026-03-09.

How to Think: Discovery → Understanding → Analysis

The most common mistake is jumping straight to queries. Instead, follow this workflow — it prevents wrong assumptions, bad joins, and wasted work.

Phase 1: Discover the Data

Before writing any analytical query, find out what you're working with.

Local files — use glob patterns to find them:

-- Find what files exist (Parquet, CSV, JSON, GeoJSON, etc.)
FROM glob('data/*.parquet');
FROM glob('**/*.csv');
FROM glob('/path/to/project/**/*.geojson');

Remote files — always load httpfs first, then probe:

INSTALL httpfs; LOAD httpfs;
-- For S3, also set the region:
SET s3_region = 'us-west-2';

-- Remote Parquet (only reads metadata, not full file)
DESCRIBE FROM 'https://example.com/data.parquet';

-- S3 / Azure / GCS
DESCRIBE FROM 's3://bucket/path/file.parquet';

-- S3 buckets with dots in the name (e.g., source.coop) need path-style URLs,
-- because virtual-hosted style breaks SSL certificate validation:
SET s3_url_style = 'path';
DESCRIBE FROM 's3://us-west-2.opendata.source.coop/repo/data.parquet';

-- Hive-partitioned datasets — check partition structure
FROM parquet_metadata('s3://bucket/dataset/**/*.parquet') LIMIT 5;

Databases — inspect what's available:

-- Attached databases
SHOW ALL TABLES;
DESCRIBE table_name;

-- External DuckDB files (new in v1.5 — no ATTACH needed)
FROM read_duckdb('other.duckdb', table_name := 'my_table');

-- External databases via ODBC (new in v1.5, requires INSTALL odbc_scanner)
-- odbc_connect(conn_str) + odbc_query(conn, sql)

Discover functions from DuckDB itself — when unsure about a function signature:

-- Search for functions by name pattern
SELECT function_name, parameters, return_type
FROM duckdb_functions() WHERE function_name LIKE 'ST_Coverage%';

-- List all extensions and their status
FROM duckdb_extensions();

-- List all settings
FROM duckdb_settings() WHERE name LIKE '%geometry%';