Oracle 11g Release 2

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BANNER
Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE 11.2.0.2.0 Production
TNS for Linux: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production

with Oppty (Acc_ID, Oppty_ID, Product1) as (
  select 123, 'JJJ', 'apples'  from dual union ALL
  select 123, 'ZZZ', 'oranges' from dual union ALL
  select 123, 'NNN', 'ananas'  from dual union ALL --adding
  select 567, 'aaj', 'apples'  from dual union ALL
  select 123, 'NNN', 'ananas'  from dual union ALL 
  select 888, 'UUU', 'berries' from dual 
)
, Acc (Acc_ID, Product2) as (
  select 123, 'apples'  from dual union all
  select 123, 'apples'  from dual union all
  select 123, 'oranges' from dual union all
  select 567, 'bananas' from dual union all
  select 567, 'grapes'  from dual union all
  select 567, 'apples'  from dual union all
  select 888, 'oranges' from dual
)
select 
  op.Acc_ID
, op.Oppty_ID
, op.Product1
, ac.Product2
, CASE WHEN EXISTS (
            SELECT 1 
            FROM Acc ac2 
            WHERE ac2.Acc_ID = op.Acc_ID 
            AND ac2.Product2 = op.Product1
            AND ROWNUM < 2 
            ) 
       THEN 'TRUE' 
       ELSE 'FALSE' 
  END cf
from Oppty op
left join Acc ac 
    on op.Acc_ID = ac.Acc_ID
ORDER BY op.Acc_ID, op.Product1 
;

ACC_ID	OPPTY_ID	PRODUCT1	PRODUCT2	CF
123	NNN	ananas	oranges	FALSE
123	NNN	ananas	apples	FALSE
123	NNN	ananas	oranges	FALSE
123	NNN	ananas	apples	FALSE
123	NNN	ananas	apples	FALSE
123	NNN	ananas	apples	FALSE
123	JJJ	apples	apples	TRUE
123	JJJ	apples	apples	TRUE
123	JJJ	apples	oranges	TRUE
123	ZZZ	oranges	apples	TRUE
123	ZZZ	oranges	oranges	TRUE
123	ZZZ	oranges	apples	TRUE
567	aaj	apples	apples	TRUE
567	aaj	apples	bananas	TRUE
567	aaj	apples	grapes	TRUE
888	UUU	berries	oranges	FALSE