Table: Friendship
+-------------+------+ | Column Name | Type | +-------------+------+ | user1_id | int | | user2_id | int | +-------------+------+ (user1_id, user2_id) is the primary key for this table. Each row of this table indicates that the users user1_id and user2_id are friends. Note that user1_id < user2_id.
A friendship between a pair of friends x and y is strong if x and 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 and the strong friendships should appear in the same order they appeared in the input..
Return the result table in any order.
The query result format is in the following example:
Friendship table: +----------+----------+ | user1_id | user2_id | +----------+----------+ | 1 | 2 | | 1 | 3 | | 2 | 3 | | 1 | 4 | | 2 | 4 | | 1 | 5 | | 2 | 5 | | 1 | 7 | | 3 | 7 | | 1 | 6 | | 3 | 6 | | 2 | 6 | +----------+----------+ Result table: +----------+----------+---------------+ | user1_id | user2_id | common_friend | +----------+----------+---------------+ | 1 | 2 | 4 | | 1 | 3 | 3 | +----------+----------+---------------+ Users 1 and 2 have 4 common friends (3, 4, 5, and 6). Users 1 and 3 have 3 common friends (2, 6, and 7). We did not include the friendship of users 2 and 3 because they only have two common friends (1 and 6).