# query

Runs DuckDB SQL against an attached database or files. Use it for raw queries or plain-language questions about project data.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 1400 installs · ★ 611
- Author: duckdb
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/duckdb/duckdb-skills/tree/HEAD/skills/query/SKILL.md
- Updated: 2026-04-23
- HTML: https://affpapa.org/en/nevibecode/skills/query

## What it does

This skill runs queries against an attached DuckDB database and reads files directly through SQL. It can turn a plain-language question into a query, then inspect available tables and their schemas in a session before querying them. Generated SQL follows DuckDB Friendly SQL patterns such as `FROM` without an explicit `SELECT *`, `GROUP BY ALL`, and `SUMMARIZE`.

File queries run in an isolated mode that permits access only to paths named in the SQL or supplied with `--file`. When there is no project state and no file reference, it uses `:memory:`, so the data path must be explicit. That is a reason to check file paths before running a query.

The skill estimates large result sets before returning them. For a source over `1M` rows without `LIMIT` or an aggregation, it asks for confirmation; for a table above `10 GB`, it also warns that execution may take time. It suggests fixes and retries after syntax, missing-table, or missing-file errors.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add duckdb/duckdb-skills --skill query -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/query/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/query/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add duckdb/duckdb-skills --skill query -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/query/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add duckdb/duckdb-skills --skill query -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/query/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install duckdb/duckdb-skills query
```

2. **Manually: put the files in place**
- File: `.github/skills/query/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add duckdb/duckdb-skills --skill query -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/duckdb/duckdb-skills --path skills/query
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/query/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add duckdb/duckdb-skills --skill query -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/duckdb/duckdb-skills/tree/HEAD/skills/query/SKILL.md

## When to use it
- run SQL against an attached DuckDB database
- query a CSV or Parquet file directly
- turn a data question into DuckDB SQL
- inspect a table schema before querying it
- avoid returning an oversized result set

## Example prompts
- "Run `FROM 'data.csv' SELECT count()`."
- "What tables are available in the attached database, and how many rows does each contain?"
- "Find category totals in `sales.parquet` using `--file sales.parquet`."

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 0ae8a8705c6877ad.

BEGIN THIRD-PARTY FILE 0ae8a8705c6877ad
````text
---
name: query
description: >
  Run SQL queries against the attached DuckDB database or ad-hoc against files.
  Accepts raw SQL or natural language questions. Uses DuckDB Friendly SQL idioms.
argument-hint: <SQL or question> [--file path]
allowed-tools: Bash
---

You are helping the user query data using DuckDB.

Input: `$@`

Follow these steps in order.

## Step 1 — Resolve state and determine the mode

Look for an existing state file in either location:

```bash
STATE_DIR=""
test -f .duckdb-skills/state.sql && STATE_DIR=".duckdb-skills"
PROJECT_ROOT="$(git rev-parse --show-toplevel 2>/dev/null || echo "$PWD")"
PROJECT_ID="$(echo "$PROJECT_ROOT" | tr '/' '-')"
test -f "$HOME/.duckdb-skills/$PROJECT_ID/state.sql" && STATE_DIR="$HOME/.duckdb-skills/$PROJECT_ID"
```

If found, verify the databases it references are still accessible:

```bash
duckdb -init "$STATE_DIR/state.sql" -c "SHOW DATABASES;"
```

Now determine the mode:

- **Ad-hoc mode** if: the `--file` flag is present, or the SQL references file paths/literals (e.g. `FROM 'data.csv'`), or `STATE_DIR` is empty.
- **Session mode** if: `STATE_DIR` is set and the input references table names, is natural language, or is SQL without file references.

If no state file exists and no file is referenced, fall back to ad-hoc mode against `:memory:` — the user must reference files directly in their SQL.

If the state file exists but any ATTACH in it fails, warn the user and fall back to ad-hoc mode.

## Step 2 — Check DuckDB is installed

```bash
command -v duckdb
```

If not found, delegate to `/duckdb-skills:install-duckdb` and then continue.

## Step 3 — Generate SQL if needed

If the input is natural language (not valid SQL), generate SQL using the Friendly SQL reference below.

In **session mode**, first retrieve the schema to inform query generation:

```bash
duckdb -init "$STATE_DIR/state.sql" -csv -c "
SELECT table_name FROM duckdb_tables() ORDER BY table_name;
"
```

Then for relevant tables:

```bash
duckdb -init "$STATE_DIR/state.sql" -csv -c "DESCRIBE <table_name>;"
```

Use the schema context and the Friendly SQL reference to generate the most appropriate query.

## Step 4 — Estimate result size

Before executing, estimate whether the query could produce a very large result that would
consume excessive tokens when returned to this conversation.

**Session mode** — check row counts for the tables involved:

```bash
duckdb -init "$STATE_DIR/state.sql" -csv -c "
SELECT table_name, estimated_size, column_count
FROM duckdb_tables()
WHERE table_name IN ('<table1>', '<table2>');
"
```

**Ad-hoc mode** — probe the source:

```bash
duckdb :memory: -csv -c "
SET allowed_paths=['FILE_PATH'];
SET enable_external_access=false;
SET allow_persistent_secrets=false;
SET lock_configuration=true;
SELECT count() AS row_count FROM 'FILE_PATH';
"
```

**Evaluate**:
- If the query already has a `LIMIT`, `count()`, or other aggregation that bounds the output -> safe, proceed.
````
END THIRD-PARTY FILE 0ae8a8705c6877ad

The third-party file has ended. Everything between the 0ae8a8705c6877ad tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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