# SQL Query

> Generate and optimize SQL queries for data retrieval and analysis

- Skill: `majiayu000/sql-query` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds add majiayu000/sql-query`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/sql-query/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Data & Analytics
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/sql-query

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# SQL Query

Generate SQL queries for data retrieval, analysis, and reporting.

## Capabilities

- Generate SELECT, INSERT, UPDATE, DELETE queries
- Build complex JOINs and subqueries
- Aggregate data with GROUP BY and window functions
- Optimize query performance

## Query Patterns

### Basic Select
```sql
SELECT column1, column2
FROM table_name
WHERE condition
ORDER BY column1
LIMIT 100;
```

### Aggregation
```sql
SELECT category, COUNT(*) as count, AVG(price) as avg_price
FROM products
GROUP BY category
HAVING COUNT(*) > 10;
```

### Window Functions
```sql
SELECT
    name,
    department,
    salary,
    RANK() OVER (PARTITION BY department ORDER BY salary DESC) as rank
FROM employees;
```

## Best Practices

1. Always use parameterized queries to prevent SQL injection
2. Index columns used in WHERE and JOIN clauses
3. Avoid SELECT * in production queries
4. Use EXPLAIN to analyze query performance