KB19481: Why are there duplicate columns in the "Column Editor-Column Selection" and why can some be deleted while some can’t? -- MicroStrategy Developer 9.x

SYMPTOM:
In the 'Column editor - Column Selection' menu, there are several columns that are duplicated. Furthermore, the Delete button is enabled for some columns and not for others. The following screenshot demonstrates this:
 
Enabled:

Disabled:

CAUSE:

• The columns appear twice because there are two Strategy Column objects (different GUID) that reference the same physical column. This can be confirmed by going to the Columns folder under System Objects:
   
  

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  NOTE: The System Objects folder is hidden by default. In order to make it visible, follow the steps in the Tech Note below:
   
  
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  KB5700-8X-3351 -- How to display hidden folders/objects in Strategy Desktop 8.x
   
  
• The reason the option to Delete one column is available for one column and not for the other is because one has dependents and the other doesn't. A simple dependency search on both columns will confirm this:
   
  AGERANGE_ID (1)
  

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  AGERANGE_ID
  

ACTION:
If this condition is posing a problem then contact Strategy Technical Support to solve the duplicate columns issue.