Problem

Table: Playback

+-------------+------+
| Column Name | Type |
+-------------+------+
| session_id  | int  |
| customer_id | int  |
| start_time  | int  |
| end_time    | int  |
+-------------+------+
session_id is the column with unique values for 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 do not intersect.

Table: Ads

+-------------+------+
| Column Name | Type |