An Oracle Database Developer designs, develops, and maintains Oracle database systems, ensuring optimal performance and security. Responsibilities include writing PL/SQL code, creating stored procedures, functions, and triggers, optimizing SQL queries, and troubleshooting database issues. They also collaborate with application developers to integrate databases with applications, perform data migrations, and ensure data integrity. Additionally, they may handle database backups, recovery, and tuning to meet business requirements while adhering to best practices and compliance standards.

To optimize a slow SQL query in Oracle, I analyze the execution plan using EXPLAIN PLAN to identify bottlenecks. I ensure proper indexing, rewrite the query for efficiency, and avoid full table scans by using WHERE clauses effectively. Partitioning large tables and materialized views can also improve performance. Additionally, I leverage Oracle hints, update statistics, and consider query restructuring or denormalization if needed. Regular monitoring and tuning using tools like AWR or SQL Tuning Advisor help maintain optimal performance.

A PL/SQL function returns a single value and can be used in SQL statements, whereas a stored procedure performs actions without returning a value directly but can use OUT parameters. Functions are typically used for computations, while procedures handle complex business logic, transactions, or DML operations. Functions must have a RETURN clause, while procedures do not. Both can accept parameters, but functions are called within expressions, while procedures are executed as standalone statements using EXEC or CALL.

Partitioning in Oracle divides large tables into smaller, manageable segments called partitions, based on criteria like range, list, or hash. This improves performance by enabling partition pruning, where only relevant partitions are scanned during queries, reducing I/O. It also enhances maintenance operations (e.g., backups, indexing) by allowing them to target specific partitions. Parallel processing and improved cache utilization further boost efficiency. Partitioning is ideal for large tables with historical data, as it optimizes query speed and resource usage while simplifying data management.

I ensure Oracle database security by implementing role-based access control (RBAC), granting minimal privileges via GRANT/REVOKE. Encryption (TDE) protects sensitive data at rest, while network encryption secures data in transit. Auditing tracks user activities, and Virtual Private Database (VPD) enforces row-level security. Regular patches mitigate vulnerabilities, and strong authentication (e.g., OID, Kerberos) prevents unauthorized access. Data masking and redaction further protect sensitive information. Compliance with standards like GDPR or HIPAA is maintained through policies, backups, and disaster recovery plans to safeguard data integrity and availability.