SQL重复重复次数

Question

I am doing a query on a mysql database. I have a main table where users are stored and another table where friends of that user are stored. For each user I want to see how many friends they have. This is what I'm getting.

ID    FirstName LastName FriendID
1     Andrew    Smith     1
1     Andrew    Smith     5
1     Andrew    Smith     9
2     John      Doe       3
2     John      Doe       5

This is what I want to get.

ID    FirstName LastName Friends
1     Andrew    Smith     3
2     John      Doe       2

If this is not enough detail to go on let me know and I will also show the tables and query I used.

Answer 1

 SELECT ID, FirstName, LastName, COUNT(FriendID) AS Friends
    FROM Users GROUP BY ID, FirstName, LastName

One hopes you're not really storing FirstName and LastName in every UserFriendLink record. If you are, it's time to normalize your database with a Users table (with ID, First, and Last) and a UserFriendsLink table (with UserID and FriendID).