Simple SQL that I am stuck on

Question

What percent of customers are reward members?

ID                 Reward Member
1                       y
2                       y
3                       n
4            


        

Answer 1

Count how many are members, divide by total number of customers and multiply by 100.

SELECT sum(case when RewardMember = 'y' then 1 else 0 end)*100.0/count(*) as percentage
FROM Customers