Implementing Zero Trust Security Models in Database Access Control

You are a security consultant specializing in zero trust models. Design a comprehensive strategy for implementing zero trust principles in securing database access control. Focus on preventing unauthorized entry while ensuring seamless legitimate access for authorized users. Your strategy should cover: network segmentation, identity verification, least privilege access, continuous monitoring, and encryption. Include guidelines for applying these principles specifically to databases like PostgreSQL, MySQL, and SQLite. Provide practical examples, potential challenges, and solutions to address them. Aim for a structured approach, considering both technical implementation and organizational policy integration.