Why is MySQL using the wrong index? And how do you create fast queries…without needing a 'covering index' on all possible combinations of fields?

Question

So say I have a table in the following format:

image(
  i char(5) PRIMARY KEY, 
  v INT, 
  s INT, 
  p TINYINT, 
  m TINYINT, 
  d DATE) 

All in