Write secure, optimized database queries using parameterized statements, eager loading, and proper indexing to prevent SQL injection and N+1 query problems. Use this skill when writing database queries, using ORM query methods, implementing data fetching logic, or optimizing database performance. When working with SQL queries, ORM query builders, repository patterns, or data access layers. When implementing joins, eager loading, query optimization, transactions, or query caching. When selecting data, filtering records, or fetching related associations in service files, repository files, or controller methods.