How to design functionality to comment about a user joining a Facebook group

database-design

User A joined the group DBA

The table responsible for users x groups is "Following" table.

    user_id      group_id
       1             1
       1             2
       2             1

And in my app I have a table Comments. the foreign key of it is polimorphic, because comments can happen inside posts, photos, etc..

      text       parent_type      parent_id  
     "cool"         Post             1
     "nice pic"     Photo            2
     "welcome!"     Following        3

It is a good schema? The following table has_many comments?

And a more complex one would be: "How to comment on a set of people joining?"

enter image description here

Best Answer

I think if you want to be able to comment on someone joining a group, then "join a group" must be an entity that can be referenced by other records. You might want to have another "parent_type" called "event" and one of the event types would be "joined a group". That would let you reference it from your comments table.

Related Solutions

Mysql – SQL DB design to support user feeds (in application like facebook)

Get rid of ambiguous columns like object_id. Use log_type to determine what you are querying on. So something like:

CREATE TABLE logs (
    log_id bigint AUTO_INCREMENT, -- not sure if this is the mysql syntax
    user_id int references users(id),
    post_id bigint references posts(id)
);

A second point is I would suggest changing the friend/unfriend to be immediate so it doesn't hit this table. This should be only for logging actions to posts, not friendships and the like. If you must log and propagate, create a separate table for this.

Design question about student assessment data

The first thing you want to do to keep your thinking straight is to choose some clear terminology. You are using the word "assessment" in two different contexts: (i) a Test and (ii) the results for a student taking the test. I understand that "test" may not be the best term, since you might be assessing based on lots of different kinds of work. The important thing is that you need to clearly differentiate between a measuring instrument and the results of an individual student against that measuring instrument.

Keeping these concepts separate will help you to keep your thinking straight when designing your database.

I'd recommend that all of your RESULTS be kept in a single table. That will make things like report cards easier to handle. Whether the result is a percentage, a letter grade or a pass/fail, you probably want to have a common representation (percentage is a good lowest common denominator) and a weight to help you aggregate marks across assessments.

Best Answer

Related Solutions

Mysql – SQL DB design to support user feeds (in application like facebook)

Design question about student assessment data

Related Question