INDEX_COL (Transact-SQL)

database_name

Is the name of the database.

schema_name

Is the name of the schema to which the index belongs.

table_or_view_name

Is the name of the table or indexed view. table_or_view_name must be delimited by single quotation marks and can be fully qualified by database name and schema name.

index_id

Is the ID of the index. index_ID is int.

key_id

Is the index key column position. key_ID is int.

nvarchar (128)

Returns NULL on error or if a caller does not have permission to view the object.

A user can only view the metadata of securables that the user owns or on which the user has been granted permission. This means that metadata-emitting, built-in functions such as INDEX_COL may return NULL if the user does not have any permission on the object. For more information, see Metadata Visibility Configuration and Troubleshooting Metadata Visibility.

A. Using INDEX_COL to return an index column name

USE AdventureWorks2008R2;
GO
SELECT 
    INDEX_COL (N'AdventureWorks2008R2.Sales.SalesOrderDetail', 1,1) AS
        [Index Column 1], 
    INDEX_COL (N'AdventureWorks2008R2.Sales.SalesOrderDetail', 1,2) AS
        [Index Column 2]
;
GO

Index Column 1      Index Column 2
-----------------------------------------------
SalesOrderID        SalesOrderDetailID

Reference