Select Record Between Date Gap-Oracle 11g, Windows 2008 server

Question

hello everyone,
I have a sql query where I need to select only records with an 18 month gap between max(date) and previous date( no dates between max(date)
and 18 month gap date), when I run the below query it should only select supid 130, not 120 (even though 120 does contain an 18 month gap date it also has a date that is less then the 18 month gap( '25-NOV-2012','DD-MON-YYYY').
how would get the query to look back 18 months for the next date and evaluate the month_between.
any help is greatly appreciated.
example:
create table supply(supID number(8), supply varchar2(20), supdate Date,supamount number(13,2));
insert into supply values(100,'Tapes',to_date('01-AUG-2013','DD-MON-YYYY'),50.00);
insert into supply values(100,'TV',to_date('01-APR-2013','DD-MON-YYYY'),250.00);
insert into supply values(100,'Discs',to_date('25-DEC-2012','DD-MON-YYYY'),25.00);
insert into supply values(120,'Tablets',to_date('25-AUG-2013','DD-MON-YYYY'),15.00);
insert into supply values(120,'Paper',to_date('25-NOV-2012','DD-MON-YYYY'),35.00);
insert into supply values(120,'Clips',to_date('20-NOV-2010','DD-MON-YYYY'),45.00);
insert into supply values(120,'Binders',to_date('28-FEB-2012','DD-MON-YYYY'),25.00);
insert into supply values(130,'Discs',to_date('25-JUL-2013','DD-MON-YYYY'),75.00);
insert into supply values(130,'Calc',to_date('25-JAN-2012','DD-MON-YYYY'),15.00);
insert into supply values(130,'Pens',to_date('15-DEC-2011','DD-MON-YYYY'),55.00);
   select * from supply p where to_char(p.supdate,'yyyy')='2013'
   and p.supid in(select s.supid from supply s where months_between(s.supdate,p.supdate)<-18)
     SUPID SUPPLY               SUPDATE    SUPAMOUNT
       120 Tablets              25-AUG-13         15
       130 Discs                25-JUL-13         75

Answer 1

Something like this?
select
from (
select
  supid
, supply
, supdate
, supamount
, lead(supdate) over (partition by supid order by supdate desc) ldate
from supply
where
months_between(supdate,ldate) >= 18
SUPID
SUPPLY
SUPDATE
SUPAMOUNT
LDATE
130
Discs
07/25/2013
75
01/25/2012
Ok. i see you want only he diff to max date.
select
from (
select
  supid
, supply
, supdate
, supamount
, lead(supdate) over (partition by supid order by supdate desc) ldate
, row_number() over (partition by supid order by supdate desc) rn
from supply
where
months_between(supdate,ldate) >= 18
and
rn = 1
Message was edited by: chris227
extended