A guide to using DuckDB from the command line. DuckDB is a small database that can query files such as CSV, Parquet, and JSON with SQL, a language for asking questions of data.

It helps run SQL against data files, open databases, read groups of files, convert or display results in several formats, and use read-only mode.

It avoids loading files into a separate database or application before inspecting, filtering, summarising, or converting them.

duckdb-en — Skill for Claude Code and Codex by aliyun

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add aliyun/alibabacloud-rds-openapi-mcp-server --skill duckdb-cli-ai-skills

Clone the repo

git clone --depth 1 https://github.com/aliyun/alibabacloud-rds-openapi-mcp-server

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/aliyun/alibabacloud-rds-openapi-mcp-server/duckdb-cli-ai-skills/github.svg)](https://agentmods.dev/skills/aliyun/alibabacloud-rds-openapi-mcp-server/duckdb-cli-ai-skills)

Your own site

<a href="https://agentmods.dev/skills/aliyun/alibabacloud-rds-openapi-mcp-server/duckdb-cli-ai-skills"><img src="https://agentmods.dev/badge/skills/aliyun/alibabacloud-rds-openapi-mcp-server/duckdb-cli-ai-skills/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/aliyun/alibabacloud-rds-openapi-mcp-server/duckdb-cli-ai-skills"><img src="https://agentmods.dev/badge/skills/aliyun/alibabacloud-rds-openapi-mcp-server/duckdb-cli-ai-skills.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 63 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,789 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector warn 7 Sept 2026

SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

medium Rogue Agent · line 236
Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.

Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00063	$0.01789
Opus 5	$0.00032	$0.00894
Sonnet 5	$0.00013	$0.00358
Haiku 4.5	$0.00006	$0.00179

Measured 12d ago against content hash abfa85cbbc2b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

duckdb-en scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skill/duckdb-cli-ai-skills/SKILL.md · 281 lines

How it starts

The opening of the file, as written. The whole thing — 281 lines — stays where its author put it; the contents beside it link to each section on GitHub.

DuckDB CLI Specialist

Helps with data analysis, SQL queries and file conversion via DuckDB CLI.

Quick Start

Read data files directly with SQL

# CSV
duckdb -c "SELECT * FROM 'data.csv' LIMIT 10"

# Parquet
duckdb -c "SELECT * FROM 'data.parquet'"

# Multiple files with glob
duckdb -c "SELECT * FROM read_parquet('logs/*.parquet')"

# JSON
duckdb -c "SELECT * FROM read_json_auto('data.json')"

Open persistent databases

# Create/open database
duckdb my_database.duckdb

# Read-only mode
duckdb -readonly existing.duckdb

Command Line Arguments

Output formats (as flags)

Flag	Format
`-csv`	Comma-separated
`-json`	JSON array
`-table`	ASCII table
`-markdown`	Markdown table
`-html`	HTML table
`-line`	One value per line

Execution arguments

Argument	Description
`-c COMMAND`	Run SQL and exit
`-f FILENAME`	Run script from file
`-init FILE`	Use alternative to ~/.duckdbrc
`-readonly`	Open in read-only mode
`-echo`	Show commands before execution
`-bail`	Stop on first error
`-header` / `-noheader`	Show/hide column headers
`-nullvalue TEXT`	Text for NULL values
`-separator SEP`	Column separator

Data Conversion

CSV to Parquet

duckdb -c "COPY (SELECT * FROM 'input.csv') TO 'output.parquet' (FORMAT PARQUET)"

Parquet to CSV

duckdb -c "COPY (SELECT * FROM 'input.parquet') TO 'output.csv' (HEADER, DELIMITER ',')"

JSON to Parquet

duckdb -c "COPY (SELECT * FROM read_json_auto('input.json')) TO 'output.parquet' (FORMAT PARQUET)"

Convert with filtering

duckdb -c "COPY (SELECT * FROM 'data.csv' WHERE amount > 1000) TO 'filtered.parquet' (FORMAT PARQUET)"

Dot Commands

Schema inspection

Command	Description
`.tables [pattern]`	Show tables (with LIKE pattern)
`.schema [table]`	Show CREATE statements
`.databases`	Show attached databases

Read the full file on GitHub · 281 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

12d ago First seen · 281 lines · 63 tokens per session scan A abfa85cbbc2b

Subscribe to this mod's changes

duckdb-en is a skill published in the GitHub repository aliyun/alibabacloud-rds-openapi-mcp-server (55 stars, last pushed 25d ago), licensed Apache-2.0. It adds 63 tokens to every session and 1,789 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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