Today, I received a call from friend asking how he can find out which database object belongs to which filegroup.

Well to find out this information can be achieved by writing a simple query using the following system catalogues: sys.filegroups, sys.indexes, sys.database_files and sys.data_spaces.

For example, here is my version of the query to return this information:

-- The following two queries return information about 
-- which objects belongs to which filegroup
SELECT OBJECT_NAME(i.[object_id]) AS [ObjectName]
    ,i.[index_id] AS [IndexID]
    ,i.[name] AS [IndexName]
    ,i.[type_desc] AS [IndexType]
    ,i.[data_space_id] AS [DatabaseSpaceID]
    ,f.[name] AS [FileGroup] 
    ,d.[physical_name] AS [DatabaseFileName]
FROM [sys].[indexes] i
INNER JOIN [sys].[filegroups] f
    ON f.[data_space_id] = i.[data_space_id]
INNER JOIN [sys].[database_files] d
    ON f.[data_space_id] = d.[data_space_id]
INNER JOIN [sys].[data_spaces] s
    ON f.[data_space_id] = s.[data_space_id]
WHERE OBJECTPROPERTY(i.[object_id], 'IsUserTable') = 1
ORDER BY OBJECT_NAME(i.[object_id])
    ,f.[name]
    ,i.[data_space_id]
GO

See the sample output generated by this query, when I executed against AdventureWork2012 sample database.

I hope you will find the information return by this query useful.