How do you design a database schema for a new application?

To design a database schema, follow these steps:

1. Identify the entities and relationships in the system and map them to tables and columns.
2. Determine the data types for each column and ensure that they are appropriate for the data they will store.
3. Consider normalization to reduce data redundancy and improve data integrity.
4. Define constraints such as primary keys, foreign keys, unique constraints, and check constraints to enforce data integrity.
5. Consider security and access control, such as user permissions and data encryption.
6. Test the schema using sample data to ensure that it meets the requirements of the application.
7. Refine the schema as needed based on feedback and testing.

It is important to consider scalability, performance, and maintainability throughout the design process, and to document the schema and any decisions made during the design process.