As a developer tasked with managing schema evolution in MySQL databases, how do you approach the challenge of preserving existing relationships while making necessary modifications to the schema? Can you share any strategies, best practices, or experiences you have encountered in dealing with this issue? Additionally, what tools or techniques do you find helpful in ensuring a smooth transition during schema evolution without compromising data integrity or application functionality?

I look forward to hearing your insights and learning from your experiences in handling schema evolution in MySQL databases.