SELECT		custID
FROM		@Sample
GROUP BY	custID
HAVING		MIN(CASE WHEN amount = 0 AND ppFlag = 'true' THEN 1 ELSE 0 END) = 1

CREATE TABLE	#Sample
	(
		custID INT,
		custName VARCHAR(4),
		mnth CHAR(6),
		ppFlag VARCHAR(5),
		amount INT
	)

INSERT	#Sample
SELECT	1234, 'ABCD', 'Jan 08', 'True', 900 UNION ALL
SELECT	1234, 'ABCD', 'MAR 08', 'True', 0 UNION ALL
SELECT	1234, 'ABCD', 'Jun 08', 'True', 0 UNION ALL
SELECT	1234, 'ABCD', 'Aug 08', 'True', 0 UNION ALL
SELECT	2345, 'XYZ', 'Jan 08', 'True', 0 UNION ALL
SELECT	2345, 'XYZ', 'FEB 08', 'True', 0 UNION ALL
SELECT	2345, 'XYZ', 'SEP 08', 'True', 0 UNION ALL
SELECT	6789, 'PQRS', 'Jan 08', 'True', 0 UNION ALL
SELECT	6789, 'PQRS', 'Jun 08', 'True', 100 UNION ALL
SELECT	6789, 'PQRS', 'OCT 08', 'FALSE', 1000 UNION ALL
SELECT	6789, 'PQRS', 'NOV 08', 'False', 500

create index ix_sample on #sample (custid, ppflag, amount)

-- Habingl
select custid from #Sample where amount = 0 and ppflag = 'true'
and custid not in (
select custid from #Sample where amount <> 0 or ppflag = 'false'
)

-- Madhi
select custid from #Sample as t1 where amount = 0 and ppflag = 'true'
and not exists
(select * from #Sample where (amount <> 0 or ppflag = 'false') and custid=t1.custid)

-- Peso
SELECT		custID
FROM		#Sample
GROUP BY	custID
HAVING		MIN(CASE WHEN amount = 0 AND ppFlag = 'true' THEN 1 ELSE 0 END) = 1

drop table #sample