Who are the players played both in NHL and WHA. List the given name and first year they were in NHL and first year in WHA.
first year they were in NHL refers to firstNHL; first year in WHA refers to firstWHA; play in both refers to firstNHL IS NOT NULL AND firstWHA IS NOT NULL

SELECT nameGiven, firstNHL, firstWHA FROM Master WHERE firstNHL IS NOT NULL AND firstWHA IS NOT NULL