EAV database model is fully in normalized form. Each column’s value is stored in their respective data type table which makes it more complex as they have to join 5-6 tables even if you need only one detail. In EAV, columns are called attributes.

Flat model uses just one table. It is not normalized and uses more database space. It is not good for dynamic requirements where you may have to add some more columns in future. Its performance is fast as it needs only one query instead of joining 5-6 tables. In flat model, columns are called fields.