Compare dates between 2 different rows and columns

create table test (ROWID int, Customer_ID  varchar(15),  PART_ID varchar(15),  Effective_Date datetime, Discontinue_Date datetime)

Insert into test values 
     (53, '00018','MCL001950','2012-01-17','2013-04-01')
, (54130, '00018','MCL001950','2013-04-02','2013-09-24')
, (65089, '00018','MCL001950','2013-09-25','2013-04-01')
, (48021, '20515','MCL001950','2013-01-17','2014-04-01')
, (58521, '20515','MCL001950','2014-04-02','2013-09-24')
, (72092, '20515','MCL001950','2012-09-25','2016-04-01')
, (64028, '36988','MCL001950','2014-05-28','2016-09-24')
, (73019, '36988','MCL001950','2014-09-25','2016-04-01')

;with mcyte as (
select *,Lead (Effective_Date)  OVER (PARTITION BY Customer_ID,PART_ID  ORDER BY Effective_Date ASC) Effective_Date_below
 From test)

 Select ROWID,Customer_ID ,PART_ID,Effective_Date, Discontinue_Date, Effective_Date_below from mcyte 
 WHERE datediff(day,Effective_Date,Effective_Date_below)<0


drop table test