+-------------+------+
|Column Name |Type|+-------------+------+
| session_id | int || customer_id | int || start_time | int || end_time | int |+-------------+------+
session_id is the columnwithuniquevaluesfor this table.
customer_id is the ID of the customer watching this session.
The session runs during the **inclusive** interval between start_time and end_time.
It is guaranteed that start_time <= end_time and that two sessions for the same customer donotintersect.
Table: Ads
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+-------------+------+
|Column Name |Type|+-------------+------+
| ad_id | int || customer_id | int ||timestamp| int |+-------------+------+
ad_id is the columnwithuniquevaluesfor this table.
customer_id is the ID of the customer viewing this ad.
timestampis the moment of time at which the ad was shown.
Write a solution to report all the sessions that did not get shown any ads.
Input:
Playback table:+------------+-------------+------------+----------+| session_id | customer_id | start_time | end_time |+------------+-------------+------------+----------+|1|1|1|5||2|1|15|23||3|2|10|12||4|2|17|28||5|2|2|8|+------------+-------------+------------+----------+Ads table:+-------+-------------+-----------+| ad_id | customer_id | timestamp |+-------+-------------+-----------+|1|1|5||2|2|17||3|2|20|+-------+-------------+-----------+Output:
+------------+| session_id |+------------+|2||3||5|+------------+Explanation:
The ad with ID 1 was shown to user 1 at time 5while they were in session 1.The ad with ID 2 was shown to user 2 at time 17while they were in session 4.The ad with ID 3 was shown to user 2 at time 20while they were in session 4.We can see that sessions 1 and 4 had at least one ad. Sessions 2,3, and 5 did not have any ads, so we return them.