Category: SQL Server

The file group information of both Index and a Table is stored in the sys.indexes table. You might wonder how the tables file group is stored in sys.indexes metadata table. It is because when ever a clustered index is created on a table in SQL Server the physical data pages of the table will be made part of the clustered index i.e. the leaf nodes of the clustered index contain the physical table data. So the clustered index file group is the file group of the table.

If there is no clustered index on the table then it is represented as a HEAP with index_id equal to ZERO in sys.indexes table.

A clustered index is always the index with index_id equal to 1 and a non clustered index will always have index_id greater than 1 in sys.indexes table .

Below query gets the file group of the table Employee in HumanResources schema of AdventureWorks database.

SELECT d.name AS FileGroup FROM sys.filegroups d JOIN sys.indexes i ON i.data_space_id = d.data_space_id JOIN sys.tables t ON t.object_id = i.object_id WHERE i.index_id<2 — could be heap or a clustered table AND t.name= 'Employee' AND t.schema_id = schema_id('HumanResources')

And below query gets the file group of the index ‘AK_Employee_rowguid’ on Employee table in HumanResources schema of AdventureWorks database.

SELECT d.name AS FileGroup FROM sys.filegroups d JOIN sys.indexes i ON i.data_space_id = d.data_space_id JOIN sys.tables t ON t.object_id = i.object_id WHERE i.name = 'AK_Employee_rowguid' AND t.name= 'Employee' AND t.schema_id = schema_id('HumanResources')

Please note that schema_id is important otherwise both the queries might return multiple results if you have same table name on different schemas.

Hope it helps

🙂 ranjith 🙂