rc-sql

A guide for reviewing relational databases, which store data in linked tables, using SQL, the language for querying them. It covers query performance, table design, safety, and database changes, with analysis read-only by default.

In plain words
What is it for?
Use it to investigate slow queries, missing indexes, repeated database requests, pagination, table structure, constraints, transactions, locks, and migrations.
Why use it?
It helps avoid guessing when a query is slow or a schema needs changes by checking the real tables, indexes, and execution plans first.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/rodolfochicone/rc-project/rc-sql
Any agent
npx skills add rodolfochicone/rc-project --skill rc-sql
Clone the repo
git clone --depth 1 https://github.com/rodolfochicone/rc-project

Made for: Claude Code, Codex.

Per session 38 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 506 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00038 $0.00506
Opus 5 $0.00019 $0.00253
Sonnet 5 $0.00008 $0.00101
Haiku 4.5 $0.00004 $0.00051

Measured 2d ago against content hash 7a3c88235ecd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

rc-sql 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 2d 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.

skills/promoted/rc-sql/SKILL.md · 34 lines

What it actually says

Banco de dados (SQL) — guias por tarefa

Guias práticos de SQL. Leia o guia da tarefa em references/ antes de agir — cada um traz o checklist, os comandos de verificação e os critérios de aceite. Sempre leia o schema e os índices reais (via \d, information_schema ou o DDL do repo) antes de recomendar qualquer mudança; não presuma a estrutura. Os exemplos usam PostgreSQL, mas os princípios valem para qualquer banco relacional.

Roteamento

Tarefa Guia
Otimização de queries (EXPLAIN, índices, N+1, paginação) references/query-optimization.md
Design de schema (normalização, tipos, constraints, chaves) references/schema-design.md
Segurança e execução (transações, locks, migrations, produção) references/safety.md

Princípios sempre válidos

  • Meça com EXPLAIN antes de otimizar — não adivinhe. Nenhum ajuste de índice ou query se justifica sem o plano de execução real na frente.
  • O índice certo bate a query esperta. Antes de reescrever uma query complexa, verifique se falta um índice.
  • Read-only por padrão (Rule 9). Para análise, só SELECT/EXPLAIN; escrita e DDL vão no relatório como recomendação, para o usuário executar ou autorizar. O hook db-guard bloqueia escrita via psql/mysql/sqlite3 no Bash — é rede de segurança, não a regra: acesso via MCP passa por fora dele.
  • O schema é o alicerce. Corrija o schema antes de contornar sua falha em código (validação duplicada, joins gambiarra, etc.).

Error Handling

  • Sem acesso ao banco: analise o schema/DDL e as queries do repositório estaticamente e diga explicitamente que o EXPLAIN real e a verificação de índices ficaram pendentes.
Files

What ships with it

3 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.

  1. 2d ago First seen · 34 lines · 38 tokens per session scan A 7a3c88235ecd

Subscribe to this mod's changes

rc-sql is a skill published in the GitHub repository rodolfochicone/rc-project (19 stars, last pushed 27d ago), licensed MIT. It adds 38 tokens to every session and 506 once invoked, about $0.0002 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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