Db2 Developer-C 11.1

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create table calendar
( dt date not null primary key
);


     
insert into calendar (dt)
with t (dt) as ( values cast('2020-01-01' as date)
                 union all
                 select dt + 1 day from t where dt < '2020-01-11')
select dt from t                 
;

create table balance 
( dt date not null
, amount int not null
,     primary key (dt)
);
    
insert into balance (dt, amount)
values ('2020-01-03',100) ,('2020-01-05', -50);

        
select c.dt, last_value(b.amount, 'IGNORE NULLS') over (order by c.dt)
from calendar c
left join balance b
    on c.dt = b.dt;


DT
2


2020-01-01
null

2020-01-02
null

2020-01-03
100

2020-01-04
100

2020-01-05
-50

2020-01-06
-50

2020-01-07
-50

2020-01-08
-50

2020-01-09
-50

2020-01-10
-50

2020-01-11
-50


create table balance1 
( cid int not null
, dt date not null
, amount int not null
, primary key (cid, dt)
);
insert into balance1 (cid, dt, amount)
values (1, '2020-01-03',100) ,(1, '2020-01-05', -50)
     , (2, '2020-01-04',75), (2, '2020-01-08',55), (2, '2020-01-10', -35);
select cid, c.dt, last_value(b.amount, 'IGNORE NULLS') over (partition by cid 
                                                        order by c.dt)
from calendar c
left join balance1 b
    on c.dt = b.dt
ORDER BY c.dt, cid
;


CID
DT
3


null
2020-01-01
null

null
2020-01-02
null

1
2020-01-03
100

2
2020-01-04
75

1
2020-01-05
-50

null
2020-01-06
null

null
2020-01-07
null

2
2020-01-08
55

null
2020-01-09
null

2
2020-01-10
-35

null
2020-01-11
null


SELECT def.cid, c.dt, LAST_VALUE(b.amount, 'IGNORE NULLS') OVER(PARTITION BY def.cid ORDER BY c.dt)
  FROM calendar c
    INNER JOIN (SELECT DISTINCT cid FROM balance1) AS def(cid) ON 1=1
    LEFT JOIN balance1 b ON (c.dt, def.cid) = (b.dt, b.cid)
  ORDER BY c.dt, def.cid
;


CID
DT
3


1
2020-01-01
null

2
2020-01-01
null

1
2020-01-02
null

2
2020-01-02
null

1
2020-01-03
100

2
2020-01-03
null

1
2020-01-04
100

2
2020-01-04
75

1
2020-01-05
-50

2
2020-01-05
75

1
2020-01-06
-50

2
2020-01-06
75

1
2020-01-07
-50

2
2020-01-07
75

1
2020-01-08
-50

2
2020-01-08
55

1
2020-01-09
-50

2
2020-01-09
55

1
2020-01-10
-50

2
2020-01-10
-35

1
2020-01-11
-50

2
2020-01-11
-35


select cid, dt, last_value(amount, 'IGNORE NULLS') over (partition by cid order by dt)
from (
  select cid, dt, amount from balance1
  union
  select distinct b.cid, c.dt, null 
  from balance1 b
  cross join calendar c
  where not exists (
    select 1 from balance1 
    where dt = c.dt and cid = b.cid
  )
) t  
order by dt, cid
;


CID
DT
3


1
2020-01-01
null

2
2020-01-01
null

1
2020-01-02
null

2
2020-01-02
null

1
2020-01-03
100

2
2020-01-03
null

1
2020-01-04
100

2
2020-01-04
75

1
2020-01-05
-50

2
2020-01-05
75

1
2020-01-06
-50

2
2020-01-06
75

1
2020-01-07
-50

2
2020-01-07
75

1
2020-01-08
-50

2
2020-01-08
55

1
2020-01-09
-50

2
2020-01-09
55

1
2020-01-10
-50

2
2020-01-10
-35

1
2020-01-11
-50

2
2020-01-11
-35
DT	2
2020-01-01	null
2020-01-02	null
2020-01-03	100
2020-01-04	100
2020-01-05	-50
2020-01-06	-50
2020-01-07	-50
2020-01-08	-50
2020-01-09	-50
2020-01-10	-50
2020-01-11	-50