sql-pro
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).
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/jeffallan/claude-skills --skill sql-pro- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads sql-pro automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
Security audits
Independent scans of the skill's instructions and bundled files.
SKILL.md
The instructions your agent reads when the skill is triggered.
SQL Pro
Core Workflow
- Schema Analysis - Review database structure, indexes, query patterns, performance bottlenecks
- Design - Create set-based operations using CTEs, window functions, appropriate joins
- Optimize - Analyze execution plans, implement covering indexes, eliminate table scans
- Verify - Run
EXPLAIN ANALYZEand confirm no sequential scans on large tables; if query does not meet sub-100ms target, iterate on index selection or query rewrite before proceeding - 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
-- 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
Window Function Pattern
-- Running total and rank within partition — no self-join required
SELECT
department_id,
employee_id,
salary,
SUM(salary) OVER (PARTITION BY department_id ORDER BY hire_date) AS running_payroll,
RANK() OVER (PARTITION BY department_id ORDER BY salary DESC) AS salary_rank
FROM employees;
EXPLAIN ANALYZE Interpretation
-- PostgreSQL: always use ANALYZE to see actual row counts vs. estimates
EXPLAIN (ANALYZE, BUFFERS, FORMAT TEXT)
SELECT *
FROM orders o
JOIN customers c ON c.id = o.customer_id
WHERE o.created_at > NOW() - INTERVAL '30 days';
Key things to check in the output:
- Seq Scan on large table → add or fix an index
- actual rows ≫ estimated rows → run
ANALYZE <table>to refresh statistics - Buffers: shared hit vs read → high
readcount signals missing cache / index
Before / After Optimization Example
-- BEFORE: correlated subquery, one execution per row (slow)
SELECT order_id,
(SELECT SUM(quantity) FROM order_items oi WHERE oi.order_id = o.id) AS item_count
FROM orders o;
-- AFTER: single aggregation join (fast)
SELECT o.order_id, COALESCE(agg.item_count, 0) AS item_count
FROM orders o
LEFT JOIN (
SELECT order_id, SUM(quantity) AS item_count
FROM order_items
GROUP BY order_id
) agg ON agg.order_id = o.id;
-- Supporting covering index (includes all columns touched by the query)
CREATE INDEX idx_order_items_order_qty
ON order_items (order_id)
INCLUDE (quantity);
Constraints
MUST DO
- Analyze execution plans before recommending optimizations
- Use set-based operations over row-by-row processing
- Apply filtering early in query execution (before joins where possible)
- Use EXISTS over COUNT for existence checks
- Handle NULLs explicitly in comparisons and aggregations
- Create covering indexes for frequent queries
- Test with production-scale data volumes
MUST NOT DO
- Use SELECT * in production queries
- Use cursors when set-based operations work
- Ignore platform-specific optimizations when targeting a specific dialect
- Implement solutions without considering data volume and cardinality
Output Templates
When implementing SQL solutions, provide:
- Optimized query with inline comments
- Required indexes with rationale
- Execution plan analysis
- Performance metrics (before/after)
- Platform-specific notes if applicable
Maintained by @jeffallan, Principal Consultant at Synergetic Solutions
FAQ
What does the sql-pro skill do?
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).
How do I install sql-pro?
Run npx skills add https://github.com/jeffallan/claude-skills --skill sql-pro in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/sql-pro/ (personal) or .claude/skills/sql-pro/ (project).
Which AI agents can use sql-pro?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is sql-pro safe to install?
Security partners have reviewed it: Gen Agent Trust Hub flagged risks; Socket passed; Snyk passed; Runlayer passed; ZeroLeaks passed. As with any skill, read the SKILL.md and bundled scripts before installing.
Who maintains sql-pro?
It is published by jeffallan in jeffallan/claude-skills. It has 6,463 recorded installs.
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