How to insert a constructed XML nodes in XQuery?

问题

I want to insert a node using below code but if i will rerun the code i don't want my node to be repeated twice-

let $doc := fn:doc("abc.xml")

(: abc.xml looks like--

<root>
  <value1>somevalue</value1>
  <value2>somevalue</value2>
  <value3>somevalue</value3>
  <value4>somevalue</value4>
  <value5>Australia</value5>
  <value6>India</value6>
  <value7>USA</value7>
  <value8>somevalue</value8>
  <value9>somevalue</value9>
  <value10>somevalue</value10>
</root> :)

let $element :=  element Root{
                    element A{"A"},
                    element B{"B"},
                    element C{"C"},
                    element D{"D"},
                    element E{"E"}
                }  

let $doc := xdmp:node-insert-after(doc("abc.xml")//value4, $element) 
return doc("abc.xml")

Whenever i am running this query my ELEMENT is getting inserted after value4 but i want that if i am running this multiple times then my element should get inserted only once and not multiple times.

Example- If i am running this 2 times-

Actual Output-

<root>
<value1>somevalue</value1>
<value2>somevalue</value2>
<value3>somevalue</value3>
<value4>somevalue</value4>
<Root>
    <A>A</A>
    <B>B</B>
    <C>C</C>
    <D>D</D>
    <E>E</E>
</Root>
<Root>
    <A>A</A>
    <B>B</B>
    <C>C</C>
    <D>D</D>
    <E>E</E>
</Root>
<value5>Australia</value5>
<value6>India</value6>
<value7>USA</value7>
<value8>somevalue</value8>
<value9>somevalue</value9>
<value10>somevalue</value10>
</root>

Expected Output-

<root>
<value1>somevalue</value1>
<value2>somevalue</value2>
<value3>somevalue</value3>
<value4>somevalue</value4>
<Root>
    <A>A</A>
    <B>B</B>
    <C>C</C>
    <D>D</D>
    <E>E</E>
</Root>
<value5>Australia</value5>
<value6>India</value6>
<value7>USA</value7>
<value8>somevalue</value8>
<value9>somevalue</value9>
<value10>somevalue</value10>
</root>

Any Suggestions ??

回答1:

Before inserting the node, check that it's not already there:

if (empty(child::Root)) then xdmp:update....

回答2:

Note that you are using xdmp:node-insert-after -- this will do what the function name says (insert after) each time its called. As commented, you can conditionally call xdmp:node-update instead. Alternatively you can use xquery directly:

doc("file.xml" )/root ! <root>{ ./*[ . << ./value4] , $element , $a/value4, ./*[. >> ./value4] }</root>

Note: the "<<" operator compares "document order" (position not value)

来源：https://stackoverflow.com/questions/52403757/how-to-insert-a-constructed-xml-nodes-in-xquery

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