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Tip of the Day
Language: XML
Expertise: Advanced
Jan 15, 2008

Using the << and >> XQuery Operators

When you want to determine the order of articles into an sequence returned by an XQuery query, you can use the << and >> operators:

    - X << Y: is true if X is before Y;
    - X >> Y: is true if Y is before X;
For example, suppose you have the following sequence of strings:

Shark, Daisy, Hunter, Lego, Helly
Use this query:

let $xml:=doc(?file:///C://Data_Local//xml//AirWings.xml?)
for $a in $xml/company/aircrafts
  for $b in  $xml/company/aircrafts
   return(if($a/type<<$b/type) then concat($a/type/@M,"--]",$b/type/@M)
 	else concat($a/type/@M,"[--",$b/type/@M)
   )
The query returns:

Shark[--Shark, Shark--]Daisy, Shark--]Hunter, Shark--]Lego,
Shark--]Helly, Daisy[--Shark, Daisy[--Daisy, Daisy--]Hunter,
Daisy--]Lego, Daisy--]Helly, Hunter[--Shark, Hunter[--Daisy,
Hunter[--Hunter, Hunter--]Lego, Hunter--]Helly, Lego[--Shark,
Lego[--Daisy, Lego[--Hunter, Lego[--Lego, Lego--]Helly ,
Helly[--Shark, Helly[--Daisy, Helly[--Hunter, Helly[--Lego,
Helly[--Helly
Leonard Anghel
 
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