How do I prevent duplicates, in XSL?

Question

How do I prevent duplicate entries into a list, and then ideally, sort that list? What I\'m doing, is when information at one level is missing, taking the information from

Answer 1

The following XSLT 1.0 transformation does what you are looking for

 
  

  
  

  
  
    
      
    
  

  
  
    
      
      
        
        
          
          
        
      
      
    
  

  
  
    
    
      , 
    
  

Returns

  
    154, 156
    Clinic Building
    1947
  
  
    
      156
      3
    
  
  
    
      156
      Contact prints
    
  
  
    
      154
      Negatives
    
  

The generate-id() = generate-id(key(...)[1]) part is what's called Muenchian grouping. Unless you can use XSLT 2.0, this is the way to go.