create table customer(customer_id int, account_id int);
insert into customer values(1,10);
insert into customer values(2,20);
 
create table contact (account_id int, time_stamp timestamp);
insert into contact values(10,CURRENT_TIMESTAMP);
insert into contact values(10,CURRENT_TIMESTAMP-1);
insert into contact values(20,CURRENT_TIMESTAMP);
insert into contact values(20,CURRENT_TIMESTAMP-1);
 
 
SELECT Customer.customer_id, Customer.Account_ID, Contact.Account_ID, Contact.Time_stamp
FROM Customer
INNER JOIN Contact ON Customer.Account_ID = Contact.Account_ID
WHERE Contact.Time_stamp = (SELECT MAX(C.Time_stamp) FROM Contact C WHERE C.Account_ID = Contact.Account_ID);
 

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