Problem Description –
A friendship between a pair of friends
y is strong if
y have at least three common friends.
Write an SQL query to find all the strong friendships.
Note that the result table should not contain duplicates with
user1_id < user2_id.
Return the result table in any order.
The query result format is in the following example.
Problem Link – Strong Friendship
Difficulty Level – Medium
with f as ( select user1_id, user2_id from Friendship union select user2_id user1_id, user1_id user2_id from Friendship ) select a.user1_id, a.user2_id, count(c.user2_id) common_friend from Friendship a join f b on a.user1_id = b.user1_id # u1 friends join f c on a.user2_id = c.user1_id # u2 friends and b.user2_id = c.user2_id # u1 u2 common friends group by a.user1_id, a.user2_id having count(c.user2_id) >= 3