---
title: "UnknownMember (MDX) | Microsoft Docs"
ms.date: 06/04/2018
ms.prod: sql
ms.technology: analysis-services
ms.custom: mdx
ms.topic: reference
ms.author: owend
ms.reviewer: owend
author: minewiskan
---
# UnknownMember (MDX)


  Returns the unknown member associated with a level or member.  
  
## Syntax  
  
```  
  
Member expression syntax  
Member_Expression.UnknownMember  
  
Hierarchy_expression syntax  
Hierarchy_Expression.UnknownMember  
```  
  
## Arguments  
 *Member_Expression*  
 A valid Multidimensional Expressions (MDX) expression that returns a member.  
  
 *Hierarchy_Expression*  
 A valid Multidimensional Expressions (MDX) expression that returns a hierarchy.  
  
## Remarks  
 Analysis Services creates an unknown member to associate fact table data with a hierarchy when the hierarchy is not known. The unknown member can be at one of the following levels:  
  
-   At the top level for attribute hierarchies that are not aggregated.  
  
-   At the first level below the **All** level for natural hierarchies.  
  
-   At any level for unnatural hierarchies.  
  
 If a member expression is specified, the **UnknownMember** function returns the unknown member child of the specified member. If the specified member does not exist, the function returns null.  
  
 If a hierarchy expression is specified, the **UnknownMember** function returns the unknown member at the top level if one exists.  
  
 If the unknown member does not exist on the level or member, the **UnknownMember** function creates a null member.  
  
> [!NOTE]  
>  If the unknown member does not exist on the hierarchy or member, an error is generated.  
  
## Examples  
 The following example returns the unknown member for the All Products member in the Product attribute hierarchy for all members of the Measures dimension.  
  
```  
SELECT [Product].[Product].[All Products].UnknownMember  
    ON Columns,  
[Measures].Members  
    ON Rows  
FROM [Adventure Works]  
  
```  
  
 The following example returns the unknown member for the Product Categories hierarchy for all members of the Measures dimension.  
  
```  
SELECT [Product].[Product Categories].UnknownMember  
    ON Columns,  
[Measures].Members  
    ON Rows  
FROM [Adventure Works]  
  
```  
  
## See Also  
 [MDX Function Reference (MDX)](../mdx/mdx-function-reference-mdx.md)