[Old Pedant]

Zergi is more than right.

He didn't make his point strong enough, if anything.

I have to make the DB such that everytime I add a user, a set of tables must be inserted (e.g 30 days, one table for each day)

This is probably *THE VERY WORST DESIGN* I have seen for a database in the last 14 years of answering database questions in various forum.

The *ONLY* point where I disagree, in a minor way, with Zergi is here:

id, user_id, channel_id, watch_time

The id column there is completely unneeded. It serves no purpose, at all.

For this table, the combination of the other three fields forms a perfect PRIMARY KEY and should be so code:

CREATE TABLE channel_watch (
    user_id INT NOT NULL,
    channel_id INT NOT NULL,
    watch_time DATETIME NOT NULL,
    PRIMARY KEY ( used_id, channel_id, watch_time ),
    CONSTRAINT FOREIGN KEY user_id REFERENCES users(user_id),
    CONSTRAINT FOREIGN KEY channel_id REFERENCES channels(channel_id)
) ENGINE INNODB;