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.

MySQL is popular because of its excellent performance and ease of use and maintenance. 1. Create database and tables: Use the CREATEDATABASE and CREATETABLE commands. 2. Insert and query data: operate data through INSERTINTO and SELECT statements. 3. Optimize query: Use indexes and EXPLAIN statements to improve performance.

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.

The difference and connection between SQL and MySQL are as follows: 1.SQL is a standard language used to manage relational databases, and MySQL is a database management system based on SQL. 2.SQL provides basic CRUD operations, and MySQL adds stored procedures, triggers and other functions on this basis. 3. SQL syntax standardization, MySQL has been improved in some places, such as LIMIT used to limit the number of returned rows. 4. In the usage example, the query syntax of SQL and MySQL is slightly different, and the JOIN and GROUPBY of MySQL are more intuitive. 5. Common errors include syntax errors and performance issues. MySQL's EXPLAIN command can be used for debugging and optimizing queries.

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.

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.

Oracle software can improve performance in a variety of ways. 1) Optimize SQL queries and reduce data transmission; 2) Appropriately manage indexes to balance query speed and maintenance costs; 3) Reasonably configure memory, optimize SGA and PGA; 4) Reduce I/O operations and use appropriate storage devices.

Learning Java requires learning basic syntax, object-oriented programming, collection frameworks, exception handling, multithreading, I/O streaming, JDBC, network programming, and advanced features such as reflection and annotation. 1. The basic syntax includes variables, data types, operators and control flow statements. 2. Object-oriented programming covers classes, objects, inheritance, polymorphism, encapsulation and abstraction. 3. The collection framework involves ArrayList, LinkedList, HashSet, and HashMap. 4. Exception handling ensures program robustness through try-catch block. 5. Multithreaded programming requires understanding of thread life cycle and synchronization. 6. I/O streams are used for data reading, writing and file operations. 7. JDBC is used to interact with databases. 8. Network programming passes S