To safely and thoroughly uninstall MySQL and clean all residual files, follow the following steps: 1. Stop MySQL service; 2. Uninstall MySQL packages; 3. Clean configuration files and data directories; 4. Verify that the uninstallation is thorough.

Oracle is not only a database company, but also a leader in cloud computing and ERP systems. 1. Oracle provides comprehensive solutions from database to cloud services and ERP systems. 2. OracleCloud challenges AWS and Azure, providing IaaS, PaaS and SaaS services. 3. Oracle's ERP systems such as E-BusinessSuite and FusionApplications help enterprises optimize operations.

MongoDB is suitable for unstructured data and high scalability requirements, while Oracle is suitable for scenarios that require strict data consistency. 1.MongoDB flexibly stores data in different structures, suitable for social media and the Internet of Things. 2. Oracle structured data model ensures data integrity and is suitable for financial transactions. 3.MongoDB scales horizontally through shards, and Oracle scales vertically through RAC. 4.MongoDB has low maintenance costs, while Oracle has high maintenance costs but is fully supported.

The main difference between MySQL and Oracle is licenses, features, and advantages. 1. License: MySQL provides a GPL license for free use, and Oracle adopts a proprietary license, which is expensive. 2. Function: MySQL has simple functions and is suitable for web applications and small and medium-sized enterprises. Oracle has powerful functions and is suitable for large-scale data and complex businesses. 3. Advantages: MySQL is open source free, suitable for startups, and Oracle is reliable in performance, suitable for large enterprises.

The difference between MySQL and Oracle in performance and scalability is: 1. MySQL performs better on small to medium-sized data sets, suitable for fast scaling and efficient reading and writing; 2. Oracle has more advantages in handling large data sets and complex queries, suitable for high availability and complex business logic. MySQL extends through master-slave replication and sharding technologies, while Oracle achieves high availability and scalability through RAC.

MySQL uses GPL and commercial licenses for small and open source projects; Oracle uses commercial licenses for enterprises that require high performance. MySQL's GPL license is free, and commercial licenses require payment; Oracle license fees are calculated based on processors or users, and the cost is relatively high.

In different application scenarios, choosing MongoDB or Oracle depends on specific needs: 1) If you need to process a large amount of unstructured data and do not have high requirements for data consistency, choose MongoDB; 2) If you need strict data consistency and complex queries, choose Oracle.

The key to learning Java without taking detours is: 1. Understand core concepts and grammar; 2. Practice more; 3. Understand memory management and garbage collection; 4. Join online communities; 5. Read other people’s code; 6. Understand common libraries and frameworks; 7. Learn to deal with common mistakes; 8. Make a learning plan and proceed step by step. These methods can help you master Java programming efficiently.