MY SQL || SOLUTION
GROUP BY:\n\nselect actor_id, director_id \nfrom(\nselect actor_id,director_id, \ncount(timestamp) as cooperated \nfrom ActorDirector \ngroup by actor_id,direct
***GROUP BY:***\n```\nselect actor_id, director_id \nfrom(\nselect actor_id,director_id, \ncount(timestamp) as cooperated \nfrom ActorDirector \ngroup by actor_id,director_id) \ntable1\nwhere cooperated>=3;\n```\n\n***GROUP WITH HAVING CLAUSE:***\n```\nselect actor_id,director_id\nfrom ActorDirector \ngroup by actor_id,director_id\nHaving count(timestamp)>=3;\n```\n\n**EXPLANATION:**\n```\n+-------------+-------------+-------------+\n| actor_id    | director_id | timestamp   |\n+-------------+-------------+-------------+\n| 1           | 1           | 0           |\n| 1           | 1           | 1           |\n| 1           | 1           | 2           |\n| 1           | 2           | 3           |\n| 1           | 2           | 4           |\n| 2           | 1           | 5           |\n| 2           | 1           | 6           |\n+-------------+-------------+-------------+\n\nGroup by actor_id, director_id:\n+-------------+-------------+-------------+\n| actor_id    | director_id | timestamp   |\n+-------------+-------------+-------------+\n| 1           | 1           | 0, 1, 2    |\n| 1           | 2           | 3, 4        |\n| 2           | 1           | 5. 6        |\n+-------------+-------------+-------------+\n\nGroup by actor_id, director_id\nHaving count(timestamp)>=3\n\n| actor_id    | director_id | count(timestamp)  |\n+-------------+-------------+-------------+\n| 1           | 1           |                3                         |\n| 1           | 2           |                2                         |\n| 2           | 1           |                2                         |\n+-------------+-------------+-------------+\n\nselect actor_id, director_id from:\n\n| actor_id    | director_id  \n+-------------+---------+\n| 1           | 1                    |\n+-------------+---------+\n\n```\n\n***PLEASE UPVOTE IF YOU FIND IT A LITTLE BIT HELPFUL, MEANS A LOT ;)***
['MySQL']