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Question

I know this question might sound a little cheesy but this is the first time I am implementing a "tagging" feature to one of my project sites and I want to make sure I do everything right.

Right now, I am using the very same tagging system as in SO.. space seperated, dash(-) combined multiple words. so when I am validating a user-input tag field I am checking for

1. Empty string (cannot be empty)
2. Make sure the string doesnt contain particular letters (suggestions are welcommed here..)
3. At least one word
4. if there is a space (there are more than one words) split the string
5. for each splitted, insert into db

I am missing something here? or is this roughly ok?

Answer 1

I've never implemented a tagging system, but am likely to do so soon for a project I'm working on. I'm primarily a database guy and it occurs to me that for performance reasons it may be best to relate your tagged entities with the tag keywords via a resolution table. So, for instance, with example tables such as:

TechQuestion
TechQuestionID (pk)
SubjectLine
QuestionBody

TechQuestionTag
TechQuestionID (pk)
TagID (pk)
Active (indexed)

Tag
TagID (pk)
TagText (indexed)

... you'd only add new Tag table entries when never-before-used tags were used. You'd re-associate previously provided tags via the TechQuestionTag table entry. And your query to pull TechQuestions related to a given tag would look like:

SELECT
q.TechQuestionID,
q.SubjectLine,
q.QuestionBody
FROM
Tag t INNER JOIN TechQuestionTag qt
ON t.TagID = qt.TagID AND qt.Active = 1
INNER JOIN TechQuestion q
ON qt.TechQuestionID = q.TechQuestionID
WHERE
t.TagText = @tagText

... or what have you. I don't know, perhaps this was obvious to everyone already, but I thought I'd put it out there... because I don't believe the alternative (redundant, indexed, text-tag entries) wouldn't query as efficiently.