Question

suppose I needed to design a database for a bulltin-board website.
something like stackoverflow which means there is a topic and a series of posts
but, no threaded posts (not a tree-based design)

I thought about two main options:

1. Topic table and Post table. Post has “topic_id” field
2. no Topic table. only one big Post table.

what do you think is the more preferable option?

Answer 1

Well, stackoverflow is a tagged based design, where a post may have multiple topics/tags.

So to capture this in a relational-style design, you would have three tables:

1. POST (post_id, author, etc.)
2. TOPIC (topic_id, name, etc.)
3. POSTTOPIC (post_id, topic_id)

The reason for POSTTOPIC is because a post may have multiple tags. Using #3, it becomes easy to assign/unassign tags to a post or to find posts with certain topics. None of which a column in POST would be able to accommodate.