如何正确迁移非标准化和不一致的用户数据库

I'm currently working in a startup which somehow neglected their infrastructure and database. Our user database is a mess (Thx to WordPress) and I am currently working to migrate it to a PostgreSQL. The problem is that the data is inconsistent. For instance some users don't have a postal address, postal address format change over time, others have their email instead of their phone number for their username...I'm currently working in a startup which someho