List the 3 highest salaries of players in the NL in 2001.
SELECT salary FROM salary WHERE YEAR   =   2001 and league_id  =  "NL" ORDER BY salary DESC LIMIT 3
3 highest salaries refers to ORDER BY salary DESC LIMIT 3; players in the NL in 2001 refers to WHERE YEAR = 2001 AND league_id = 'NL';