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info: I have a table full of songs full of data (artist, songname, link, etc). I want to set up a [very POWRful] relationship with tags. In the end, I want to search by tag and return a playlist of relevant songs. here is what I was thinking: (rough pseudo code): TABLE songs( id int(16) primary index, ... ) TABLE tags ( id int(16) primary index, ... ) TABLE taggedAs ( songId int(16), tagId int(16), songId foreign key songs(id), tags foreign key tags(id) ) however these seems sucky because whenever i want to tag a new song, i need to operate on each table if I could use something like mongodb (such goodness), i would just store an array of tagnames on the songs. also, it'd be nice to have related tags, but I don't know if that is possible with this design.
Hmm... Yes, it's true that you'll have to basically insert into tags if the relevant tag doesn't exist, etc. I believe you could also drop the tags table and make taggedAs have a songId and a tag. List of tags for a given song: SELECT DISTINCT tag FROM taggedAs WHERE songId = 15 List of existing tags: SELET DISTINCT tag FROM taggedAs List of songs with a given tag: SELECT songs.* FROM taggedAs JOIN songs ON songs.id = songId But, honestly, when doing most lookup operations (which are typically far more frequent then write operations for tagging), I believe your table layout with some JOINs will be more performant.
Probably also want to create a table which lists tags and which tags they relate to. It all depends on how you want to develop the project. Start by laying out all your data for a couple of related songs, look for where you can reduce duplication and go from there. Use the normalization levels as a guide.
this is a really scary picture