Generic design: char vs varchar primary keys

Hi,

Can you point me to any pages that explain the difference between using, 
say CHAR(8) vs VARCHAR(8) as the primary key for a table?  Is there any 
impact on the database in terms of:

- Speed of indexed retrieval
- Speed of join from a referencing table
- Storage (I presume VARHAR(8) would have a slight edge, in general)
- Any other issue

Regards,

-- Raj
-- 
Raj Mathur                raju@kandalaya.org      http://kandalaya.org/      GPG: 78D4 FC67 367F 40E2 0DD5  0FEF C968
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