Design Pattern to add columns in database table dynamically

Question

The user wants to add new fields in UI dynamically. This new field should get stored in database and they should be allowed to perform CRUD on it.

Now I can do this

Answer 1

Find out what the maximum number of user-added fields will be and add them before hand. For example 'User1', 'User2', 'User3', 'User4'...etc. You can then enable the fields on the UI based on some configurable settings.