how many members are under age 30?
select count(*) from member where age < 30
how about the number of members with a black membership card?
select count(*) from member where membership_card = 'Black'
what is the total number between these two groups of members?
select count(*) from member where membership_card = 'Black' or age < 30
what are their ids and names?
select name, member_id from member where membership_card = 'Black' or age < 30