How To Find Fragmentation Of Indexes

Hi

I try to find the percentage of fragmentation in the perticular table using the following table. For some tables it is getting the results but for some database tables it is saying the error in qurey even if I use same query. Is there any reason for that. Or is there any other way to find out the fragmentation of table. any help would be fine. Thanks!


SELECT a.index_id, name, avg_fragmentation_in_percent

FROM sys.dm_db_index_physical_stats (DB_ID(), OBJECT_ID(N'schema.tablename),

NULL, NULL, NULL) AS a

JOIN sys.indexes AS b ON a.object_id = b.object_id AND a.index_id = b.index_id;

GO

And is there any way to find out when did index rebuild occurs in perticular index or table. Thank you very much.