Implementation Of The Following?

Tell me how to implement the mechanism following'and notification about new posts.

Interested in the implementation details at the database level. Use MySQL as a relational DBMS to apply is not possible.

The problem arose from the fact that the user who signed on, for example, the comments to the record shows the count of new comments and it is unclear how decremented or reset this counter when viewing the comments.
October 3rd 19 at 04:38
1 answer
October 3rd 19 at 04:40
I can advise that:
To make a table "user"-"record"-"last view".
When the user comes to the entry, set the current time.
To obtain the number of the new review, the request is made: "if the date of review more than the date of the last view". Etc.
New review of all records is taken as well.

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