Which PROC SQL query will remove duplicate values of MemberType from the query output, so that only the unique values are listed?
proc sql nodup; select membertype from sasuser.frequentflyers;
proc sql; select distinct(membertype) as MemberType from sasuser.frequentflyers;
proc sql; select unique membertype from sasuser.frequentflyers group by membertype;
proc sql; select distinct membertype from sasuser.frequentflyers;