select c.name as 'client_name',cs.client_id,max(cs.sub_date) as 'date_sub',cs.sub_price from client c ,
client_subscription cs where cs.client_id=c.id group by cs.client_id,cs.sub_price;

要获得每个客户端的客户端订阅，可以使用自连接

select c.name, a.client_id, a.date_sub, a.sub_price
from client_subscription a
join (
    select client_id, max(date_sub) date_sub
    from client_subscription
    group by client_id
) b on a.client_id = b.client_id and a.date_sub = b.date_sub
join client c on a.client_id = c.id
order by a.date_sub

演示
或使用左连接

select c.name, a.client_id, a.date_sub, a.sub_price
from client_subscription a
left join client_subscription b on a.client_id = b.client_id and a.date_sub < b.date_sub
join client c on a.client_id = c.id
where b.client_id is null
order by a.date_sub

演示
使用更新的数据集更新查询

select c.full_name, a.icid, a.date_sub, a.sub_price
from internetclientdetails a
join (
    select icid, max(date_sub) date_sub
    from internetclientdetails
    group by icid
) b on a.icid = b.icid and a.date_sub = b.date_sub
join internetclient c on a.icid = c.id
order by a.date_sub;

select c.full_name, a.icid, a.date_sub, a.sub_price
from internetclientdetails a
left join internetclientdetails b on a.icid = b.icid and a.date_sub < b.date_sub
join internetclient c on a.icid = c.id
where b.icid is null
order by a.date_sub

更新的演示

试试这个

SELECT c.Name, c.id , MAX(date_sub), sub_price  FROM client c LEFT JOIN client_subscription c_s on c.id=c_s.client_id
GROUP BY c.id
ORDER BY c.id ASC

嗨，试试下面的样品也许对你有帮助。

DECLARE @tblClient AS TABLE (ID INT , Name varchar(100))
DECLARE @tblClientSub As TABLE (id INT,client_id INT,date_sub DATE,sub_price INT)

INSERT INTO @tblClient (id,Name)
VALUES 
(1,'Linda'),
(2,'Mary'),
(3,'Joe')  

INSERT INTO @tblClientSub(Id,client_id ,    date_sub ,    sub_price)
VALUES
(1,1,'2018/01/01',50),
(2,2,'2018/02/01',50),
(3,2,'2018/03/01',30),
(4,2,'2018/04/01',30),
(5,3,'2018/01/01',50),
(6,3,'2018/07/01',50),
(7,1,'2018/02/01',40)

SELECT c.Id,c.Name,cs.date_sub,cs.sub_price
FROM @tblClient c
CROSS APPLY (SELECT TOP (1)date_sub,sub_price 
             FROM @tblClientSub 
             WHERE client_id = c.Id 
             ORDER BY date_sub DESC) cs