Question

I have the option of writing two different formats for a database structure:

Article ------- ArticleID int FK  Article_Tags ------------ ArticleTagID int FK ArticleID int FK TagText varchar(50) 

or

Article ------- ArticleID int PK  Article_Tags ------------ ArticleTagID int PK ArticleID int FK TagText varchar(50) FK  Tag --- TagText varchar(50) PK 

If I want a list of all tags in the database, I could use:

select distinct tagtext from article_tags 

or:

select tagtext from tag 

The first situation is pretty easy. Maybe it would speed up if i indexed it properly. The second is a little harder because I have to constantly delete tags with no joins. Imagine a pretty large system, which would be better.

Answer 1

I would go with

Article ------- ArticleID int PK  Article_Tags ------------ ArticleTagID int PK ArticleID int FK TagId int FK  Tag --- TagId int identity(1,1) PK TagText varchar(50)  

There really is no reason to denormalize this from get go. (your first and second versions are not normalized)

Having tags in a separate table is fine, and getting the unique tags is cleaner without that distinct statement.

Performance wise if any of the 3 options are going to perform pretty much the same provided the correct indexing is applied.