MySQL is an open source relational database management system, mainly used to store, organize and retrieve data. Its main application scenarios include: 1. Web applications, such as blog systems, CMS and e-commerce platforms; 2. Data analysis and report generation; 3. Enterprise-level applications, such as CRM and ERP systems; 4. Embedded systems and Internet of Things devices.

To develop a complete Python Web application, follow these steps: 1. Choose the appropriate framework, such as Django or Flask. 2. Integrate databases and use ORMs such as SQLAlchemy. 3. Design the front-end and use Vue or React. 4. Perform the test, use pytest or unittest. 5. Deploy applications, use Docker and platforms such as Heroku or AWS. Through these steps, powerful and efficient web applications can be built.

Avoiding SQL injection in PHP can be done by: 1. Use parameterized queries (PreparedStatements), as shown in the PDO example. 2. Use ORM libraries, such as Doctrine or Eloquent, to automatically handle SQL injection. 3. Verify and filter user input to prevent other attack types.

Java middleware is a software that connects operating systems and application software, providing general services to help developers focus on business logic. Typical applications include: 1. Web server (such as Tomcat and Jetty), which handles HTTP requests; 2. Message queue (such as Kafka and RabbitMQ), which handles asynchronous communication; 3. Transaction management (such as SpringTransaction), which ensures data consistency; 4. ORM framework (such as Hibernate and MyBatis), which simplifies database operations.

There are three ways to verify the correctness of SQL files: 1. Use DBMS's own tools, such as mysql command line tools; 2. Use special SQL syntax checking tools, such as SQLLint; 3. Use IDEs such as IntelliJIDEA or VisualStudioCode; 4. Write automated scripts for checking.

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.

Lock waiting issues can be solved by optimizing SQL statements, using appropriate transaction isolation levels, and monitoring database performance. 1. Optimize SQL statements to reduce lock holding time, such as improving query efficiency through indexing and partitioning. 2. Choose the appropriate transaction isolation level to avoid unnecessary lock waiting. 3. Monitor database performance and promptly discover and deal with lock waiting problems.

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