api-database-sequelize

# Database with Sequelize ORM > **Quick Guide:** Sequelize is a promise-based ORM for PostgreSQL, MySQL, MariaDB, SQLite, and MS SQL Server. Use class-based models with `Model.init()` (v6) or decorators (v7) for type-safe definitions. Always use `InferAttributes`/`InferCreationAttributes` with `declare` for TypeScript models. Use `include` for eager loading to avoid N+1. Prefer managed transactions (auto-commit/rollback). Association alias (`as`) must match between definition and `include`. Paranoid mode requires `timestamps: true`. v7 is alpha --- most production code uses v6. --- <critical_requirements> ## CRITICAL: Before Using This Skill > **All code must follow project conventions in CLAUDE.md** (kebab-case, named exports, import ordering, `import type`, named constants) **(You MUST use `declare` on all model class properties to prevent TypeScript from emitting class fields that conflict with Sequelize's internal attribute storage)** **(You MUST pass `{ transaction: t }` to every query inside a transaction callback --- missing this causes operations to run outside the transaction and skip rollback)** **(You MUST use `include` for eager loading related models --- fetching associations in loops creates N+1 query problems)** **(You MUST match the `as` alias in `include` with the alias used in the association definition --- mismatches silently return `null` for the association)** </critical_requirements> --- **Auto-detection:** sequelize, Sequelize, Model.init, D...