[SQL手撕]

刪除重複的電子郵箱

delete from Person
where id not in
(select id from
(select min(id) as id from Person
group by email) as temp)

好友申請 II ：誰有最多的好友

select id,count(id) as num from
(select requester_id as id from RequestAccepted 
union all
select accepter_id as id from RequestAccepted) as temp
group by id
order by num desc
limit 1

買下所有產品的客戶

select customer_id from Customer 
group by customer_id 
having count(distinct product_key) = (select count(product_key ) from Product )