SELECT a.*,
case when (SELECT count(1) FROM TableA where ColumnA = a.ColumnB)=0 then 'Y'
else 'N'
end as Flag
FROM TableB a
where ColumnC = '7974'
SELECT a.*,
case when (SELECT count(1) FROM TableA where ColumnA = a.ColumnB)=0 then 'Y'
else 'N'
end as Flag
FROM TableB a
where ColumnC = '7974'