How to make additional fields in custom table?

Question

ASP.NET

What is the best way to make additional fields with a given type (string, integer, date, etc.) of data for a custom table. For example, there is a USERS table with predefined fields (first name, last name, gender), and the user himself could add his own fields to this table, for example, a phone number of the "string" type. Are there any "best practices" on this issue? I am using ASP. NET in conjunction with MS SQL

Answer 1

Neither the user nor the application software should "be able" to change the table structure. Nowhere. Unless in a shooting club shooting at one's feet and then on holidays -)
But some tables of additional attributes - yes, no problem
Alternatively:
something like a table of "additional" values ​​in the form of id_user, attr_type, row, value *
well, in addition attr_type , descr,value_type - type reference of attribute names
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* - value - it will be rather several columns of different types