SELECT string
  FROM some_table
 WHERE string = ?
    OR off_by( 1, string, ? )
    OR off_by( 2, string, ? )

##</code><code>##

string char(25)
match  char(25)
off_by int(1)

##</code><code>##

SELECT string
  FROM some_table
 WHERE string = ?
    OR ( match = ? and off_by = 1 )
    OR ( match = ? and off_by = 2 )