# SQL Pro

Optimizes SQL queries, designs database schemas, and troubleshoots performance issues.

- Repository: https://github.com/Jeffallan/claude-skills (12164 stars)
- Category: Design
- License: MIT
- Last updated: 2026-10-30
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add Jeffallan/claude-skills --skill sql-pro -g -a claude-code -y`
Codex: `npx skills add Jeffallan/claude-skills --skill sql-pro -g -a codex -y`
Cursor: `npx skills add Jeffallan/claude-skills --skill sql-pro -g -a cursor -y`
Gemini CLI: `npx skills add Jeffallan/claude-skills --skill sql-pro -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add Jeffallan/claude-skills`

## Description

Optimizes SQL queries, designs database schemas, and troubleshoots performance issues. Use when a user asks why their query is slow, needs help writing complex joins or aggregations, mentions database performance issues, or wants to design or migrate a schema. Invoke for complex queries, window functions, CTEs, indexing strategies, query plan analysis, covering index creation, recursive queries, EXPLAIN/ANALYZE interpretation, before/after query benchmarking, or migrating queries between database dialects (PostgreSQL, MySQL, SQL Server, Oracle).

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# SQL Pro

## Core Workflow

1. **Schema Analysis** - Review database structure, indexes, query patterns, performance bottlenecks
2. **Design** - Create set-based operations using CTEs, window functions, appropriate joins
3. **Optimize** - Analyze execution plans, implement covering indexes, eliminate table scans
4. **Verify** - Run `EXPLAIN ANALYZE` and confirm no sequential scans on large tables; if query does not meet sub-100ms target, iterate on index selection or query rewrite before proceeding
5. **Document** - Provide query explanations, index rationale, performance metrics

## Reference Guide

Load detailed guidance based on context:

| Topic | Reference | Load When |
|-------|-----------|-----------|
| Query Patterns | `references/query-patterns.md` | JOINs, CTEs, subqueries, recursive queries |
| Window Functions | `references/window-functions.md` | ROW_NUMBER, RANK, LAG/LEAD, analytics |
| Optimization | `references/optimization.md` | EXPLAIN plans, indexes, statistics, tuning |
| Database Design | `references/database-design.md` | Normalization, keys, constraints, schemas |
| Dialect Differences | `references/dialect-differences.md` | PostgreSQL vs MySQL vs SQL Server specifics |

## Quick-Reference Examples

### CTE Pattern
```sql
-- Isolate expensive subquery logic for reuse and readability
WITH ranked_orders AS (
    SELECT
        customer_id,
        order_id,
        total_amount,
        ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date DESC) AS rn
    FROM orders
    WHERE status = 'completed'          -- filter early, before the join
)
SELECT customer_id, order_id, total_amount
FROM ranked_orders
WHERE rn = 1;                           -- latest completed order per customer
```

The rest: https://github.com/Jeffallan/claude-skills/blob/HEAD/skills/sql-pro/SKILL.md