In MySQL, add fields using ALTERTABLEtable_nameADDCOLUMNnew_columnVARCHAR(255)AFTERexisting_column, delete fields using ALTERTABLEtable_nameDROPCOLUMNcolumn_to_drop. When adding fields, you need to specify a location to optimize query performance and data structure; before deleting fields, you need to confirm that the operation is irreversible; modifying table structure using online DDL, backup data, test environment, and low-load time periods is performance optimization and best practice.

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.

Navicat is a powerful and user-friendly database management tool for beginners and veterans. 1. It supports multiple database types and provides unified interface management. 2. Communication with the database through JDBC or ODBC to simplify operations. 3. Provide SQL editing and optimization tools to improve query efficiency. 4. Support data migration and model design to improve work efficiency.

Renaming a database in MySQL requires indirect methods. The steps are as follows: 1. Create a new database; 2. Use mysqldump to export the old database; 3. Import the data into the new database; 4. Delete the old database.

Navicat is not free, it offers a 30-day trial and paid version. 1. The trial version allows users to experience all functions and a license is required after the expiration of the period. 2. The paid version has personal, corporate and educational licenses, providing full functionality and support.

Navicat improves database workflow through core functions such as data modeling, SQL development, data transmission and synchronization. 1) Data modeling tools allow the design of database structures by dragging and dropping. 2) SQL development tools provide syntax highlighting and automatic completion to improve the SQL writing experience. 3) The data transmission function automatically handles data type conversion and consistency checks to ensure smooth data migration. 4) The data synchronization function ensures data consistency in development and production environments.