Question

I just need some advice about using tags. I’m working on a website right now and the users can post videos, images, audio and information about themselves.

I never worked with tags before on a normal website (did work with them on wordpress, youtube etc..), so I need some advise to start designing my database.

What is the common way to work with tags when you have multiple categories? Do I have to add tags for each category?
Example:

Table:
gallery

gallery_id
image
tags

Table
audio

audio_id
title
link
audio_tags

Etc... 

Or do I make only one table named “tags” and all the tags in it?
Like:
Table Tags:

tag_id
tag

Thanks in advance.

Answer 1

It depends if you want tags to be shared among multiple objects. If you want that to be separate, then i would make separate tag tables for them. If not, I would have the same tag table, and use different tables for each relation the tags will have, so

for separate:

gallery
...
gallery_tags
tag_id
tag

tags_to_gallery
tag_id
gallery_id
..same for audio..

for not separate:

  gallery
  ...
  audio
  ...
  tags
    tag_id
    tag

  gallery_to_tag
  gallery_id
  tag_id

  audio_to_tag
  audio_id
  tag_id 

you could also do this with one ploymorphic table. with a table with something like this:

tag_relations
 tag_id
 object_id
 object_table