mysql-best-practices

---
name: mysql-best-practices
description: MySQL performance optimization and best practices. Use this skill when writing, reviewing, or optimizing MySQL queries, schema designs, or database configurations.
license: MIT
---

# MySQL Best Practices

Comprehensive performance optimization guide for MySQL, adapted from PostgreSQL best practices. Contains rules across 8 categories, prioritized by impact to guide automated query optimization and schema design.

## When to Apply

Reference these guidelines when:
- Writing SQL queries or designing schemas
- Implementing indexes or query optimization
- Reviewing database performance issues
- Configuring connection pooling or scaling
- Optimizing for MySQL-specific features
- Working with MySQL security features

## Rule Categories by Priority

| Priority | Category | Impact | Prefix |
|----------|----------|--------|--------|
| 1 | Query Performance | CRITICAL | `query-` |
| 2 | Connection Management | CRITICAL | `conn-` |
| 3 | Security | CRITICAL | `security-` |
| 4 | Schema Design | HIGH | `schema-` |
| 5 | Concurrency & Locking | MEDIUM-HIGH | `lock-` |
| 6 | Data Access Patterns | MEDIUM | `data-` |
| 7 | Monitoring & Diagnostics | LOW-MEDIUM | `monitor-` |
| 8 | Advanced Features | LOW | `advanced-` |

## How to Use

Read individual rule files for detailed explanations and SQL examples:

```
references/query-missing-indexes.md
references/schema-partial-indexes.md
references/_sections.md
```

Each rule file contains:
- Brief explanation of why it matters
- Incorrect SQL example with explanation
- Correct SQL example with explanation
- Optional EXPLAIN output or metrics
- Additional context and references
- MySQL-specific notes

## Full Compiled Document

For the complete guide with all rules expanded: `AGENTS.md`

## MySQL vs PostgreSQL Key Differences

This skill adapts PostgreSQL best practices to MySQL. Key differences:

- **JSON**: MySQL uses `JSON` type (not `JSONB`), with `JSON_EXTRACT()`, `JSON_CONTAINS()` functions
- **Arrays**: MySQL doesn't have native arrays; use JSON arrays or normalized tables
- **Full-Text Search**: MySQL uses `FULLTEXT` indexes with `MATCH() AGAINST()` syntax
- **UUIDs**: Use `CHAR(36)` or `BINARY(16)` instead of native UUID type
- **String Matching**: Use `LIKE` (case-sensitive) or `LIKE BINARY` instead of `ILIKE`
- **Type Casting**: Use `CAST()` function instead of `::` operator
- **Window Functions**: MySQL 8.0+ supports window functions (similar to PostgreSQL)

## References

- https://dev.mysql.com/doc/
- https://dev.mysql.com/doc/refman/8.0/en/optimization.html
- https://dev.mysql.com/doc/refman/8.0/en/explain.html
- https://dev.mysql.com/doc/refman/8.0/en/json-functions.html
- https://dev.mysql.com/doc/refman/8.0/en/fulltext-search.html