Show all party names and the number of members in each party.
SELECT T2.party_name ,  count(*) FROM Member AS T1 JOIN party AS T2 ON T1.party_id  =  T2.party_id GROUP BY T1.party_id
party names refers to party_name; number of members in each party requires COUNT(*) with a GROUP BY on party_id; joining Member and Party tables on party_id to relate members with their parties;