Database Design: Multiple join tables or one table with identifying 'table' column

Question

I'm designing a database where any content can be tagged and I'm likely to want to be able to select all content with a specific tag.

I'm struggling with the following two options and would appreciate some advice. If there's a better way please let me know.

Option A
Multiple 'many to many' join tables.

tag:
  id
  tag

media:
  id
  title
  src
  creation

media_tags:
  id
  media_id
  tag_id

article:
  id
  title
  content
  creation

article_tags:
  id
  article_id
  tag_id

Options B
A single 'tag reference' table, which uses a 'table' column to identify which table to join to.

tag:
  id
  tag

tag_reference:
  id
  row_id
  tag_id
  table

media:
  id
  title
  src
  creation

article:
  id
  title
  content
  creation

From a maintenance point of view option B seems favorable but considering the SQL query to select all content and don't think it's possible without multiple queries.

Answer 1

When using Option B , you can't set up foreign keys to the other tables. Thus I would go with Option A and one table for each m:n relation.

"From a maintenance point of view option B" – is a nightmare. What happens if you delete an article? All the rows with that row_id will persist in tag_reference table. You always need to update those entries manually.

Answer 2

Option B contains a multivalued dependency - and as such is breach of 4th normal form . I much prefer Option A

Answer 3

Actually, It depends on every sql developer. But I prefer Option A since you can easily know that a certain column in a table is a foreign key ( assuming it's true ) of the other table.

Option B is somewhat bad design because storing table names in a column is bad idea. You can spend more IF or CASE here.

Answer 4

The second option pretty much prevents you using any JOINs for efficient SQL, forcing you into using slow multiple selects.

So I would say the first option is far preferable.