How to make SQL many-to-many same-type relationship table

Question

I\'m a newbie to SQL and I\'m jumping in head first trying to learn as much as possible as I\'m coding, which is difficult as I\'m designing the database I\'ll have to live

Answer 1

A single linking table suffices, like so:

People( PersonId bigint, Name nvarchar, etc )
Friends( FromPersonId bigint, ToPersonId bigint, DateAdded datetime )

Example queries:

Who is friends with me? (i.e. people who have added me as a friend, but not necessarily reciprocated)

SELECT
    People.Name
FROM
    Friends
    INNER JOIN People ON Friends.FromPersonId = People.PersonId
WHERE
    Friends.ToPersonId = @myPersonId

Who added me between two dates?

SELECT
    People.Name
FROM
    Friends
    INNER JOIN People ON Friends.FromPersonId = People.PersonId
WHERE
    Friends.ToPersonId = @myPersonId
    AND
    Friends.DateAdded >= @startDate
    AND
    Friends.DateAdded <= @endDate