How to design database for such a task?

Hello. The task is similar to this:
There are 4 website from which I get news. There is a user who enters a keyword. And every parish news I have to send the link to to the user if:
1) it is indicated in subscriptions this website
2) in the description of the news there is at least one keyword specified.

And I can not understand how to design the database. If you take MongoDB, it is something like this:
User = {
email: "ya@ya.ya",
sites: ["", ""],
keys: ["spirt", "sport", "music"]

If you take MySQL, you don't understand. Was thinking of making one table for each site, where one column stores a list of emails of those who signed. And in a separate table to store keywords for a user in the form of long strings, where words are separated by commas. But again not sure that this is correct.

How to be?

PS, to Clarify that sites only 4. And key words all of the users have different
June 26th 19 at 14:26
2 answers
June 26th 19 at 14:28
If you take MongoDB, it is something like this:
There's much to think ochem, rules option.

And in a separate table to store
It is unnecessary in mysql, you can do the same for mongodb
June 26th 19 at 14:30
If only four sites, and further expansion is not planned, in principle, just in a users table, adds four fields. If laid on the extension table of the users table and table subscriptions (user_id, site_id).
Keyword - either a single field with a list of such words in the user table or the same table keyword and table of when the user is the key word.
In the extreme version of the subscription table to modificeres (user_id, site_id, keyword_id) allowing the user to specify its own set of keywords for each site.

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