Oracle 18c

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select * from V$VERSION;


BANNER
BANNER_FULL
BANNER_LEGACY
CON_ID


Oracle Database 18c Express Edition Release 18.0.0.0.0 - Production
Oracle Database 18c Express Edition Release 18.0.0.0.0 - Production
Version 18.4.0.0.0
Oracle Database 18c Express Edition Release 18.0.0.0.0 - Production
0


--Результат подзапроса (отфильтрованных клиентов)
create table fq (idclient, idblank, datenter) as
    select 1, 1, date'2021-06-03'+0.5 from dual union all  
    select 5, 4, date'2021-03-13'+0.5 from dual union all 
    select 2, 1, date'2021-04-03'+0.5 from dual
    
3 rows affected

--Вся таблица
create table t (idclient, idblank, datenter) as
    select 5, 13, date'2021-01-14'+0.5 from dual union all
    select 1, 1, date'2021-06-03'+0.5 from dual union all  
    select 1, 5, date'2021-02-13'+0.5 from dual union all 
    select 2, 14, date'2021-06-03'+0.5 from dual union all  
    select 3, 12, date'2021-02-17'+0.5 from dual union all 
    select 4, 9, date'2021-04-03'+0.5 from dual union all  
    select 5, 6, date'2021-01-12'+0.5 from dual union all 
    select 6, 7, date'2021-04-03'+0.5 from dual union all  
    select 5, 4, date'2021-01-13'+0.5 from dual union all 
    select 3, 3, date'2021-04-03'+0.5 from dual union all  
    select 4, 2, date'2021-02-13'+0.5 from dual union all 
    select 2, 1, date'2021-04-03'+0.5 from dual union all
    select 1, 10, date'2021-05-25'+0.5 from dual
13 rows affected

select t2.idclient, case when t1.idblank is not null then 1 end as priz_m3
,t1.datenter
from (select 
 idclient, idblank, datenter
from t ) t1
left join (select
  t.idclient, max(t.datenter) as datenter
 from t  join fq on t.idclient=fq.idclient
 group by t.idclient
) t2 on t1.idclient=t2.idclient 
  and t2.datenter between add_months(t1.datenter,-3) and t1.datenter-1


IDCLIENT
PRIZ_M3
DATENTER


null
1
03-APR-21

null
1
03-JUN-21

null
1
03-APR-21

null
1
03-APR-21

null
1
13-FEB-21

null
1
14-JAN-21

null
1
12-JAN-21

null
1
13-JAN-21

null
1
17-FEB-21

null
1
03-APR-21

null
1
03-JUN-21

null
1
13-FEB-21

null
1
25-MAY-21

IDCLIENT	PRIZ_M3	DATENTER
null	1	03-APR-21
null	1	03-JUN-21
null	1	03-APR-21
null	1	03-APR-21
null	1	13-FEB-21
null	1	14-JAN-21
null	1	12-JAN-21
null	1	13-JAN-21
null	1	17-FEB-21
null	1	03-APR-21
null	1	03-JUN-21
null	1	13-FEB-21
null	1	25-MAY-21