probably a simple request but a rookie like me can’t seem to figure it out.

I just need a query that generates results when there is > 180 days between the TransactionDate for each MemberNumber. This is what I have so far but it’s not working correctly:

SELECT [TransactionDate]
  ,[MemberNumber]
  ,[MemberName]
  ,[PrincipalAmount]
  ,[TransactionCategory]
  ,[TransactionChannel]
  ,[Service]
  ,[Product]
  ,
  
CASE 
WHEN DATEDIFF(day, TransactionDate, TransactionDate) > 180 
AND MemberNumber = MemberNumber THEN 'Dormant'
ELSE 'Active'
END AS Dormant_Flag