ORDER BY Optimization

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http://dev.mysql.com/doc/refman/5.0/en/order-by-optimization.html


SELECT * FROM t1 
  ORDER BY key_part1,key_part2,... ;
    
SELECT * FROM t1 
  WHERE key_part1=constant 
  ORDER BY key_part2;
    
SELECT * FROM t1 
  ORDER BY key_part1 DESC, key_part2 DESC;
    
SELECT * FROM t1
  WHERE key_part1=1 
  ORDER BY key_part1 DESC, key_part2 DESC;