# Data Management

> Design and manage data storage effectively. Use when working with databases, schemas, or data migrations. Covers schema design, migrations, and data integrity.

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

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# Data Management

## Workflows

- [ ] **Schema Design**: Define tables, relationships, constraints
- [ ] **Migrations**: Version control schema changes
- [ ] **Indexing**: Add indexes for query performance
- [ ] **Backup**: Ensure data recovery capability

## Schema Design Principles

### Normalization
- **1NF**: Atomic values, no repeating groups
- **2NF**: No partial dependencies
- **3NF**: No transitive dependencies

### When to Denormalize
- Read-heavy workloads
- Reporting/analytics
- Caching layers

## Migration Best Practices

### Forward-Only Migrations
Each migration should be a single forward step.

```sql
-- migrations/001_create_users.sql
CREATE TABLE users (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  email VARCHAR(255) NOT NULL UNIQUE,
  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE INDEX idx_users_email ON users(email);
```

### Safe Migrations
- Add columns as nullable first
- Create indexes concurrently
- Never drop columns in the same deploy

## Indexing Strategy

```sql
-- B-tree (default): Equality and range queries
CREATE INDEX idx_users_email ON users(email);

-- Partial index: When you query a subset
CREATE INDEX idx_active_users ON users(id) WHERE active = true;

-- Composite index: Multiple columns
CREATE INDEX idx_orders_user_date ON orders(user_id, created_at DESC);
```

## Connection Management

```typescript
// Use connection pooling
const pool = new Pool({
  max: 20,                    // Max connections
  idleTimeoutMillis: 30000,   // Close idle connections
  connectionTimeoutMillis: 2000
});
```

## Data Integrity

- Use foreign key constraints
- Add NOT NULL where appropriate
- Use CHECK constraints for validation
- Consider using ENUM types for fixed values