title: ID fields in SQL tables: rule or law?
body: <p>Just a quick database design question: Do you ALWAYS use an ID field in EVERY table, or just most of them?  Clearly most of your tables will benefit, but are there ever tables that you might not want to use an ID field?  </p>
  
  <p>For example, I want to add the ability to add tags to objects in another table (foo).  So I've got a table FooTag with a varchar field to hold the tag, and a fooID field to refer to the row in foo.  Do I really need to create a clustered index around an essentially arbitrary ID field?  Wouldn't it be more efficient to use fooID and my text field as the clustered index, since I will almost always be searching by fooID anyway?  Plus using my text in the clustered index would keep the data sorted, making sorting easier when I have to query my data.  The downside is that inserts would take longer, but wouldn't that be offset by the gains during selection, which would happen far more often?</p>
  
  <p>What are your thoughts on ID fields?  Bendable rule, or unbreakable law?</p>
  
  <p>edit: I am aware that the example provided is not normalized.  If tagging is to be a major part of the project, with multiple tables being tagged, and other 'extras', a two-table solution would be a clear answer.  However in this simplest case, would normalization be worthwhile?  It would save some space, but require an extra join when running queries</p>