查找最小月和最大月，使用此值创建日历，将此日历与表关联：
D小提琴

with 
  dates as (select min(date_) mnd, max(date_) mxd from tbl),
  cal as (select add_months(mnd, level - 1) mth
           from dates connect by level - 1 <= months_between(mxd, mnd))
select * from cal left join tbl partition by (name) on (date_ = mth)

一个选项使用递归查询来生成日期。那你就可以了 cross join 它与 name table上有空的，最后把table拿过来 left join :

with cte (dt, max_dt) as (
    select min(dt), max(dt) from mytable
    union all
    select dt + interval '1' month, max_dt from cte where dt < max_dt
)
select c.dt, n.name, t.cnt
from cte c
cross join (select distinct name from mytable) n
left join mytable t on t.name = n.name and t.dt = c.dt
order by n.name, c.dt

请注意 date 以及 count 不是oracle中的有效标识符-我将它们重命名为 dt 以及 cnt 在查询中。
db小提琴演示：

DT        | NAME |  CNT
:-------- | :--- | ---:
01-DEC-19 | P    | null
01-JAN-20 | P    |    4
01-FEB-20 | P    | null
01-MAR-20 | P    |    3
01-APR-20 | P    | null
01-MAY-20 | P    |    2
01-JUN-20 | P    |    5
01-DEC-19 | T    |    4
01-JAN-20 | T    |    1
01-FEB-20 | T    | null
01-MAR-20 | T    | null
01-APR-20 | T    | null
01-MAY-20 | T    | null
01-JUN-20 | T    | null

可以按如下方式使用行生成器技术：

WITH DATES(DT) AS
(SELECT ADD_MONTHS(TRUNC(SYSDATE,'MON'),LEVEL-1) FROM DUAL CONNECT BY LEVEL <= 7) -- use logic as per your requirement
SELECT NM.NAME, D.DT, T.COUNT 
FROM DATES D 
JOIN (SELECT DISTINCT NAME FROM YOUR_TABLE) NM ON 1=1 --CROSS JOIN FOR CREATING 7 RECORDS FOR EACH NAMES
LEFT JOIN YOUR_TABLE T ON D.DT = T.DATE AND NM.NAME = T.NAME

insert into table_name values ("P","01/12/19","");
insert into table_name values ("P","01/02/20","");
insert into table_name values ("P","01/04/20","");
insert into table_name values ("T","01/02/20","");
insert into table_name values ("T","01/03/20","");
insert into table_name values ("T","01/04/20","");
insert into table_name values ("T","01/05/20","");
insert into table_name values ("T","01/06/20","");

然后查询： select * from table_name order by Name asc, Date asc;