actors-and-directors-who-cooperated-at-least-three-times.sql

/*

Table: ActorDirector

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| actor_id    | int     |
| director_id | int     |
| timestamp   | int     |
+-------------+---------+
timestamp is the primary key column for this table.
Write a SQL query for a report that provides the pairs (actor_id, director_id) where the actor have cooperated with the director at least 3 times.

Example:

ActorDirector table:
+-------------+-------------+-------------+
| actor_id    | director_id | timestamp   |
+-------------+-------------+-------------+
| 1           | 1           | 0           |
| 1           | 1           | 1           |
| 1           | 1           | 2           |
| 1           | 2           | 3           |
| 1           | 2           | 4           |
| 2           | 1           | 5           |
| 2           | 1           | 6           |
+-------------+-------------+-------------+

Result table:
+-------------+-------------+
| actor_id    | director_id |
+-------------+-------------+
| 1           | 1           |
+-------------+-------------+
The only pair is (1, 1) where they cooperated exactly 3 times.

*/

# V0 
select actor_id, director_id
from ActorDirector
group by actor_id, director_id
having count(1)>=3

# V1
# https://code.dennyzhang.com/actors-and-directors-who-cooperated-at-least-three-times
select actor_id, director_id
from ActorDirector
group by actor_id, director_id
having count(1)>=3

# V2 
# Time:  O(n)
# Space: O(n)
SELECT actor_id, director_id
FROM ActorDirector
GROUP BY actor_id, director_id
HAVING COUNT(1) >= 3
ORDER BY NULL