title: Effect of a long char as a primary key
body: <p>I am planning a database which has a mini chart of accounts.  My account codes are names like:</p>
  
  <ul>
  <li>CURRENT_DEBTORS</li>
  <li>CURRENT_CREDITORS</li>
  <li>CASH_AT_BANK</li>
  </ul>
  
  <p>I am thinking of using the account codes as a primary key in the account database, which would mean it would be a foreign key in a transactions table.  The field would be something like CHAR(20) in MySql.  The transactions table would get about 10,000 entries per month.</p>
  
  <p>How will this long-ish character index affect performance?  I can use a surrogate key if I have too, but would prefer not too.  (I'm not too worried about disk space, of course).</p>