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Agent skill

Grdb

by johnrogers in johnrogers/claude-swift-engineering

A skill your agent uses when writing raw SQL with GRDB, complex joins across 4+ tables, window functions, ValueObservation for reactive queries, or dropping down from SQLiteData for performance.

MITAuto-check passedDatabases

Install Grdb

skills CLI
$ npx skills add johnrogers/claude-swift-engineering --skill grdb -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install johnrogers/claude-swift-engineering grdb --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/johnrogers/claude-swift-engineering.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/swift-engineering/skills/grdb .claude/skills/grdb && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
grdb
GitHub stars
231
Token cost
~719 tokens
SKILL.md length
300 words
Files
6 (incl. references)
Skills in repo
17
Repo updated
First seen
Licence
MIT

At a glance

A skill your agent uses when writing raw SQL with GRDB, complex joins across 4+ tables, window functions, ValueObservation for reactive queries, or dropping down from SQLiteData for performance.

  • Works in 5 steps: Choose DatabaseQueue (single connection)… → Define migrations with DatabaseMigrator → Create Record types (Codable,… → …
  • Writing raw SQL with GRDB
  • SKILL.md covers Reference Loading Guide, When to Use GRDB vs SQLiteData, Core Workflow and Requirements, plus 1 more section
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Grdb is an agent skill from johnrogers/claude-swift-engineering. Use when writing raw SQL with GRDB, complex joins across 4+ tables, window functions, ValueObservation for reactive queries, or dropping down from SQLiteData for performance. Direct SQLite access for iOS/macOS with type-safe queries and migrations.

Its SKILL.md is about 720 tokens, which your agent loads only when the skill is triggered. The skill folder holds 6 other files, including reference files (for example `references/getting-started.md`, `references/migrations.md` and `references/performance.md`).

It sits in Databases, covering SQL, Type safety and iOS development. It works with SQL, SQLite, iOS and macOS. The repository describes itself as: A collection of agents and skills to aid in the planning, implementation, documentation and testing of Swift/TCA code. The licence is MIT.

When your agent uses it

  • Writing raw SQL with GRDB
  • Complex joins across 4+ tables
  • Window functions
  • ValueObservation for reactive queries

Example prompts

  • “/grdb”

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

  1. Choose DatabaseQueue (single connection) or DatabasePool (concurrent reads)
  2. Define migrations with DatabaseMigrator
  3. Create Record types (Codable, FetchableRecord, PersistableRecord)
  4. Write queries with raw SQL or QueryInterface
  5. Use ValueObservation for reactive updates

What it can do on your machine

Read from SKILL.md and the folder at commit 1dc2cf4. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • github.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Grdb loads about 719 tokens when it runs, and up to ~4.4k if it reads all its reference files. Until then it costs about 63 tokens; SKILL.md has 300 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~63
When it runs · the whole SKILL.md, loaded when a task matches
~719
With references · SKILL.md plus every file in references/, read only if the agent opens them
~4.4k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from johnrogers/claude-swift-engineering at commit 1dc2cf4, republished under its MIT licence (© johnrogers). 300 words, ~719 tokens.

Download SKILL.mdSave it as .claude/skills/grdb/SKILL.md (or your agent's skills folder). This skill also uses 5 other files; get the full folder from GitHub.
name
grdb
description
Use when writing raw SQL with GRDB, complex joins across 4+ tables, window functions, ValueObservation for reactive queries, or dropping down from SQLiteData for performance. Direct SQLite access for iOS/macOS with type-safe queries and migrations.

GRDB

Direct SQLite access using GRDB.swift - type-safe Swift wrapper with full SQLite power when you need it.

Reference Loading Guide

ALWAYS load reference files if there is even a small chance the content may be required. It's better to have the context than to miss a pattern or make a mistake.

ReferenceLoad When
Getting StartedSetting up DatabaseQueue or DatabasePool
QueriesWriting raw SQL, Record types, type-safe queries
Value ObservationReactive queries, SwiftUI integration
MigrationsDatabaseMigrator, schema evolution
PerformanceEXPLAIN QUERY PLAN, indexing, profiling

When to Use GRDB vs SQLiteData

ScenarioUse
Type-safe @Table modelsSQLiteData
CloudKit sync neededSQLiteData
Complex joins (4+ tables)GRDB
Window functions (ROW_NUMBER, RANK)GRDB
Performance-critical raw SQLGRDB
Reactive queries (ValueObservation)GRDB

Core Workflow

  1. Choose DatabaseQueue (single connection) or DatabasePool (concurrent reads)
  2. Define migrations with DatabaseMigrator
  3. Create Record types (Codable, FetchableRecord, PersistableRecord)
  4. Write queries with raw SQL or QueryInterface
  5. Use ValueObservation for reactive updates

Requirements

  • iOS 13+, macOS 10.15+
  • Swift 5.7+
  • GRDB.swift 6.0+

Common Mistakes

  1. Performance assumptions without EXPLAIN PLAN — Assuming your query is fast or slow without checking EXPLAIN QUERY PLAN is guessing. Always profile queries with EXPLAIN before optimizing.

  2. Missing indexes on WHERE clauses — Queries filtering on non-indexed columns scan the entire table. Index any column used in WHERE, JOIN, or ORDER BY clauses for large tables.

  3. Improper migration ordering — Running migrations out of order or skipping intermediate versions breaks schema consistency. Always apply migrations sequentially; never jump versions.

  4. Record conformance shortcuts — Not conforming Record types to PersistableRecord or FetchableRecord correctly leads to silent data loss or deserialization failures. Always implement all required protocols correctly.

  5. ValueObservation without proper cleanup — Forgetting to cancel ValueObservation when views disappear causes memory leaks and stale data subscriptions. Store the cancellable and clean up in deinit.

© johnrogers, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 5 other files (references) in plugins/swift-engineering/skills/grdb of johnrogers/claude-swift-engineering.

  • SKILL.md
  • references/getting-started.md
  • references/migrations.md
  • references/performance.md
  • references/queries.md
  • references/value-observation.md

Open the folder on GitHubat commit 1dc2cf4

Compare with similar skills

Grdb next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Grdb compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Grdb this skilljohnrogers/claude-swift-engineering231—~719Automated safety check: PassMIT
RevopsAvdLee/RocketSimApp8036 repos~3.7kAutomated safety check: PassCustom licence
SQL Database Support for pRESTprest/prest4.6k—~1.6kAutomated safety check: PassMIT
Cursor BYOK Database Schemaleookun/cursor-byok3.2k—~1.3kAutomated safety check: PassMIT
Squixeduardofuncao/squix273—~784Automated safety check: PassMIT
Analyzing SQL Tracesnwjs/chromium.src160—~2.9kAutomated safety check: PassBSD-3-Clause

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Works with

Categories

Questions about Grdb

What does Grdb do?

A skill your agent uses when writing raw SQL with GRDB, complex joins across 4+ tables, window functions, ValueObservation for reactive queries, or dropping down from SQLiteData for performance. Grdb is an agent skill from johnrogers/claude-swift-engineering. Use when writing raw SQL with GRDB, complex joins across 4+ tables, window functions, ValueObservation for reactive queries, or dropping down from SQLiteData for performance.

When should I use Grdb?

Grdb fits situations like: writing raw SQL with GRDB; complex joins across 4+ tables; window functions; valueObservation for reactive queries.

How do I install Grdb in Claude Code?

Run `npx skills add johnrogers/claude-swift-engineering --skill grdb -a claude-code`. Or copy the skill folder (plugins/swift-engineering/skills/grdb in johnrogers/claude-swift-engineering) into .claude/skills/grdb in your project. Claude Code loads it when a task matches its description.

How do I install Grdb in Codex?

Run `npx skills add johnrogers/claude-swift-engineering --skill grdb -a codex`. Or copy the skill folder (plugins/swift-engineering/skills/grdb in johnrogers/claude-swift-engineering) into .agents/skills/grdb in your project. Codex loads it when a task matches its description.

Can I use Grdb in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add johnrogers/claude-swift-engineering --skill grdb -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/grdb, .gemini/skills/grdb, .github/skills/grdb and .opencode/skills/grdb in your project.

What does Grdb need to run?

SKILL.md names no scripts, command-line tools or credentials: Grdb is instructions for the agent only.

Does Grdb access the network?

SKILL.md names 1 domain. As links in the text: github.com. This is read from the text; nothing was executed.

Is Grdb safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Grdb use?

Grdb is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Grdb use?

About 719 tokens (SKILL.md is roughly 2.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 3.7k tokens, read only when the agent opens those files.

What are the alternatives to Grdb?

Skills that share tags, products or a category with Grdb: Revops (AvdLee/RocketSimApp, 803 stars), SQL Database Support for pREST (prest/prest, 4.6k stars), Cursor BYOK Database Schema (leookun/cursor-byok, 3.2k stars) and Squix (eduardofuncao/squix, 273 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Grdb?

johnrogers (a GitHub user) maintains it in johnrogers/claude-swift-engineering, which has 231 GitHub stars. The repository holds 17 skills in this directory. The repository was last updated on January 18, 2026.

Source: johnrogers/claude-swift-engineering on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.