[SQL] DB Design: how to indicate if a column data is public or private

I'm designing a database and I have a question about how to make private some user data.

I have a user table, with name, city, birthday, biography, etc. And the user can make some data private (other users can see that data).

First, I thought to add columns to the table to indicate if a column is private or not. For example:

User
-------

user_id | name | city | cityIsPrivate | birthday | birthdayIsPrivate
---------+------+------+---------------+----------+------------------


Or, another approach is to add a varchar column to indicate which columns are private:

User
-------

user_id | name | city | birthday | privateColumns
---------+------+------+----------+---------------


And this privateColumns will have this: "city:NO; birthday:YES".

The user table will only have three columns that can be private or public. I will only have to add three columns more to the table.

Any advice?

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