database

Database guidance covers how to design tables and relationships, change schemas safely, improve slow queries, and manage stored records. A database is software that stores and retrieves an application's information.

In plain words
What is it for?
Use it when creating schemas, writing migrations, choosing indexes, setting transaction boundaries, reviewing ORM database access, or deciding between recoverable soft deletion and permanent deletion.
Why use it?
It helps avoid breaking migrations, unnecessary indexes, slow query patterns such as N+1 queries, and irreversible data deletion mistakes.

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/kid-sid/codex-spellbook/database
Any agent
npx skills add kid-sid/codex-spellbook --skill database
Clone the repo
git clone --depth 1 https://github.com/kid-sid/codex-spellbook

Made for: Claude Code, Codex.

Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 604 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 $0.00043 $0.00604
Opus 5 $0.00022 $0.00302
Sonnet 5 $0.00009 $0.00121
Haiku 4.5 $0.00004 $0.00060

Measured 2d ago against content hash 28206170a8f4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

database 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/database/SKILL.md · 84 lines

How it starts

The opening of the file, as written. The whole thing — 84 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Database

Model schemas for clarity, migrate in safe increments, and optimize queries around real access patterns rather than guesswork.

When to Activate

  • Design a new schema or table
  • Add or review a migration
  • Diagnose slow queries or query explosions
  • Decide whether an index is warranted
  • Refactor a transaction boundary
  • Choose data deletion semantics
  • Review ORM usage for N+1 issues

Naming and Migrations

Object Convention
Tables plural snake_case
Columns singular snake_case
Primary keys id
Foreign keys <table>_id
Join tables alphabetical plural pair, e.g. roles_users
Change Safe Pattern Avoid
Drop column add replacement, backfill, dual-read, dual-write, drop later destructive one-step drop
Rename column add new column and migrate gradually instant rename in hot path
Add constraint backfill invalid rows first applying constraint to dirty data

BAD

ALTER TABLE users DROP COLUMN full_name;

GOOD

ALTER TABLE users ADD COLUMN display_name text;
UPDATE users SET display_name = full_name WHERE display_name IS NULL;

Indexing and Query Shape

Query Pattern Index
Equality on foreign key single-column btree
Filter + sort composite index ordered by filter then sort
Case-insensitive search functional index matching query function
Signal Fix
One query per row in a list view eager load or batch fetch
Repeated lookup in serializer loop prefetch related data
ORM debug logs showing repeated shapes consolidate access path

Transactions and Deletion

Preferred Avoid
Short transaction around consistent write set Holding transaction open across network calls
Retry on known transient conflicts Blind retries on all DB errors
Use Soft Delete When Use Hard Delete When
Audit or recovery matters Regulation or retention requires full erasure
References must remain historically intact Data is ephemeral and unreferenced

Read the full file on GitHub · 84 lines

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 · 84 lines · 43 tokens per session scan A 28206170a8f4

Subscribe to this mod's changes

database is a skill published in the GitHub repository kid-sid/codex-spellbook (21 stars, last pushed 3mo ago), licensed MIT. It adds 43 tokens to every session and 604 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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