title: Index sizes in MySQL
body: <p>I am just starting to investigate optimization for my MySQL database. From what I'm reading, indexing seems like a good idea - so I am wanting to create an index on one of my <code>VARCHAR</code> columns, on a table using the <code>MyISAM</code> engine.</p>
  
  <p>From what I'm reading, I understand that an index is limited to a size of 1,000 bytes. A <code>VARCHAR</code> character is 3 bytes in size, though. Does that mean that if I want to index a <code>VARCHAR</code> column with 50 rows, I need an index prefix of 6 characters? (1,000 bytes / 50 rows / 3 bytes per character = 6.66)</p>
  
  <p>If so, that seems a little comiplicated - which is why I'm questioning my understanding. It seems pretty odd that you would only be able to index 333 rows in a <code>VARCHAR</code> column, using a prefix of 1 character.</p>
  
  <p>Am I missing something?</p>