create table t1 (tcode varchar(10), tName varchar(10));
create table t2 (idx int, tcode varchar(10), paydt varchar(10), pay_amt bigint, nextpaydt varchar(10));
insert into t1 (tcode, tname) values ('C00001', '그린마일'), ('C00002', '이지세스');
insert into t2(idx, tcode, paydt, pay_amt, nextpaydt) values
(4, 'C00001', '2020-04-20', 50000,'2020-05-20'),
(3, 'C00001', '2020-03-20', 100000,'2020-04-20'),
(2, 'C00002', '2020-01-10', 50000,'2020-02-10'),
(1, 'C00002', '2020-12-20', 100000,'2021-01-20')


select
t1.tname, t2.paydt, t2.pay_amt, t2.nextpaydt
from t1
inner join t2
on t1.tcode = t2.tcode
inner join (
select
tcode, max(idx) as idx
from
t2
group by tcode
) t3
on t2.tcode = t3.tcode
and t2.idx = t3.idx