create table customers (  
    cust_id                             number not null  primary key,  
	cust_name							varchar(100)  
)

insert into customers (  
    cust_id,  
    cust_name  
) values (  
    1234,  
    'John Doe')

insert into customers (  
    cust_id,  
    cust_name  
) values (  
    1235,  
    'Ram')

insert into customers (  
    cust_id,  
    cust_name  
) values (  
    1236,  
    'Rahim')

create table customer_review (  
	review_id	varchar2(15) not null primary key, 
    cust_id                  number,  
    remarks                           varchar2(50) not null,  
    contact_date                     date,  
    contact_time                      TIMESTAMP  
) 

insert into customer_review (  
    review_id,  
    cust_id,  
    remarks,  
    contact_date,  
    contact_time  
) values (  
    'CUST123',  
    1234,  
    'This is awsome product',  
    TO_DATE('2019-10-26','YYYY-MM-DD'),  
    TO_TIMESTAMP('26-OCT-2019 17:00:00:00','DD-MON-YYYY HH24:MI:SS:FF')  
)

insert into customer_review (  
    review_id,  
    cust_id,  
    remarks,  
    contact_date,  
    contact_time  
) values (  
    'CUST124',  
    1234,  
    'This is not good product I chnaged mind now',  
    TO_DATE('2019-10-27','YYYY-MM-DD'),  
    TO_TIMESTAMP('27-OCT-2019 17:00:00:00','DD-MON-YYYY HH24:MI:SS:FF')  
)

insert into customer_review (  
    review_id,  
    cust_id,  
    remarks,  
    contact_date,  
    contact_time  
) values (  
    'CUST125',  
    1234,  
    'After update now it is working fine',  
    TO_DATE('2019-10-27','YYYY-MM-DD'),  
    TO_TIMESTAMP('27-OCT-2019 17:00:00:00','DD-MON-YYYY HH24:MI:SS:FF')  
)

insert into customer_review (  
    review_id,  
    cust_id,  
    remarks,  
    contact_date,  
    contact_time  
) values (  
    'CUST125',  
    1235,  
    'I am new user',  
    TO_DATE('2019-10-27','YYYY-MM-DD'),  
    TO_TIMESTAMP('27-OCT-2019 17:00:00:00','DD-MON-YYYY HH24:MI:SS:FF')  
)

insert into customer_review (  
    review_id,  
    cust_id,  
    remarks,  
    contact_date,  
    contact_time  
) values (  
    'NEW123',  
    1235,  
    'I am new user',  
    TO_DATE('2019-10-27','YYYY-MM-DD'),  
    TO_TIMESTAMP('27-OCT-2019 17:00:00:00','DD-MON-YYYY HH24:MI:SS:FF')  
)

SELECT a.cust_id,b.remarks,b.contact_date,b.contact_time FROM customers a,(select * from customer_review 
where (cust_id,contact_time,contact_date) in (select cust_id, max(contact_time),max(contact_date) from customer_review group by cust_id) 
) b WHERE  a.cust_id=b.cust_id

select * from customers

select * from customer_review