Will this Post/Tag DB schema cause problems later?

Question

I'm planning a new service for my ASP.NET MVC app and want to use tags. I've never really been too fond of tags, but SO delivers so I'll give it a shot.

Here's the simplified schema I'm thinking about:

Post Table
------------------
PK PostId BigInt (or perhaps uniqueidentifier)
...more post related fields...
Tags nvarchar(200)

Then I'd LINQ query something like:

_db.Posts.Where(p => p.Tags.Contains("TagToFind"));

Obviously, this is super simple, but would do what I need. Do you see any glaring problems with this? Likely performance, I'd imagine .Contains() isn't exactly fast.

UPDATE I plan to have a pre-built array of allowable tags that the user can pick from.

Answer 1

This may work, but it will not scale unless you have a fulltext index on that column (and you query it using fulltext style queries).

Also normalizing tags (having a tags table) is kind of key, unless you do that you can not deal with merges or track when / who created what tag.

Answer 2

Do you see any glaring problems with this?

Well, let's give it a test:

INSERT INTO PostTable (PostId, Tags) 
VALUES (0, NULL), 
       (1, NULL), 
       (2, NULL), 
       (22, ''), 
       (55, 'Hello world!'), 
       (-99, 'Hello world!');

No relational key, no data integrity. No, absolutely no problems there ;)

Answer 3

Your query will not be able to use index. So, more posts => worse performance.