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71 lines
2.1 KiB
Markdown
71 lines
2.1 KiB
Markdown
# MySQL — Patterns e Anti-patterns
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> Conexão | Schemas | JSON | InnoDB | Otimização
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## Comandos Rápidos
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```bash
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mysql -h localhost -u root -p mydb
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mysql -h host -u user -p -e "SELECT NOW();" mydb
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mysql -h host -u user -p mydb < migration.sql
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```
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## Schema Design
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```sql
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CREATE TABLE users (
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id BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
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email VARCHAR(255) NOT NULL UNIQUE,
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name VARCHAR(255) NOT NULL,
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created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
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updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
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) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
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```
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> **SEMPRE** `ENGINE=InnoDB` — transações, FK, row-level locking. `utf8mb4` — suporta emoji e acentos completos.
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## JSON Ops
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```sql
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CREATE TABLE orders (
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id BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
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metadata JSON,
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FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
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);
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SELECT * FROM orders WHERE JSON_EXTRACT(metadata, '$.source') = 'web';
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-- Shorthand (MySQL 8+):
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SELECT * FROM orders WHERE metadata->>'$.source' = 'web';
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```
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## Indexes
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```sql
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-- Index composto
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CREATE INDEX idx_orders_user_id ON orders(user_id);
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-- Índice parcial (simulado com generated column + índice)
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ALTER TABLE orders ADD COLUMN is_active TINYINT(1)
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GENERATED ALWAYS AS (status != 'cancelled') STORED;
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CREATE INDEX idx_orders_active ON orders(is_active);
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```
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## Joins e Agregações
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```sql
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SELECT u.name, o.total, o.status
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FROM users u
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INNER JOIN orders o ON o.user_id = u.id
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WHERE o.created_at > '2026-01-01'
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ORDER BY o.total DESC
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LIMIT 10;
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SELECT status, COUNT(*) AS cnt, SUM(total) AS revenue
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FROM orders GROUP BY status HAVING cnt > 5;
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```
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## Diferenças principais vs PostgreSQL
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| Aspecto | MySQL | PostgreSQL |
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|---------|-------|-------------|
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| Auto-increment | `AUTO_INCREMENT` | `SERIAL` / `IDENTITY` |
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| UUID padrão | Requer plugin (não padrão) | `uuid-ossp` built-in |
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| JSON | `JSON` type (baixa performance em queries) | `JSONB` indexável |
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| CTEs | Suportado (MySQL 8+) | Nativo desde sempre |
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| Window Functions | MySQL 8+ | Nativo |
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| Transactions | InnoDB obrigatório | Sempre |
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| Null-safe join | `<=>` (spaceship operator) | `IS NOT DISTINCT FROM` |
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