# DB > Database (PostgreSQL) SQL best practices for clean, performant, and maintainable queries. Use when writing or reviewing SQL, schema changes, or database-related guidance. Use when this capability is needed. - Skill: `tomevault-io/db-4` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/db-4` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/db-4/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Data & Analytics - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/db-4 --- # Database Stack Skill ## Default guidance Use the PostgreSQL rule file in this folder as the authoritative reference. ## Workflow (use this order) 1. Confirm schema context and target tables/columns. 2. Draft query with explicit columns and clear aliases. 3. Prefer CTEs for readability and reuse. 4. Avoid `NOT IN`; use `NOT EXISTS` or `LEFT JOIN ... IS NULL`. 5. Run `explain analyze` and address sequential scans. 6. Add or adjust indexes if query plan needs them. ## Review Checklist - Naming uses `snake_case`; SQL keywords are lowercase. - Explicit joins used; no implicit joins. - `select *` avoided; columns are explicit. - `NOT IN` avoided with `NULL`-safe alternatives. - Query plan checked with `explain analyze`. ## Local Resources - `postgresql.mdc` for naming, formatting, query patterns, and performance guidance. --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/heyayushh) — claim your Tome and manage your conversions.