Should i use one table or more than one table

Question

I am having two tables pages(id,name) and posts(id,msg) In both pages and posts having id field which is auto incremented and starts from 1

I want to create like table when a user likes a post or page details should be stored in like table.

My question is should i use different like table for post and pages

  1) page_like(page_id,user_id);// (page_id,user_id) composite PK
   2) post_like(post_id,user_id);//(post_id,user_id) composite PK

or should i use

 like(element_id,element_type,liked_by) //(element_id,element_type,liked_by) composite PK

Which method should i use and why ? Is there better way to do this?

Answer 1

If you have two distinct keys that automatically increment individually for page and post, I would definitely use two separate tables. It wouldn't make sense for you two have a row that has a post and a page with two sets of distinct keys.

Answer 2

Out of the choices presented, you should definitely go with the first one. The alternative prevents you from declaring a FOREIGN KEY, and enforcing referential integrity in the application code is surprisingly difficult.

That being said, there is a third option: "inherit" both post and page from a common "super-table", then like the super-table directly. This is probably not justified for just two sub-types, but can be very useful if you anticipate your model will grow in the future. I have described the basic idea here.