How to get element type in xpath?

Question

My xml is:

<record>
  <field name="f1"/>
  <id name="f2"/>
  <id name="f3"/>
  <field name="f4"/>
  <info/>
</record>

I want to loop through it in xquery like this:

for $i in $records/record/field | $records/record/id
return
   if ( .... $i is id .... ) then .... do something .... else ... do something else ...

Is this possible? How can distinguish when $i is id and when it is field?

Answer 1

You can use a function library or create your own user defined function. Something like this:

for $i in $records/record/field | $records/record/id
return
   if (name($i)="id") then .... do something .... else ... do something else ...

http://www.xqueryfunctions.com/xq/fn_name.html

Answer 2

Check out the local-name XQuery function - see the MSDN docs here.

Given a node or a node set, it should give you the node's name - the name of the tag. I guess that's what you're looking for, right??

E.g. if you do this:

DECLARE @input XML = '<record>
  <field name="f1"/>
  <id name="f2"/>
  <id name="f3"/>
  <field name="f4"/>
  <info/>
</record>'

SELECT 
    inp.nod.query('local-name(.)')
FROM 
    @input.nodes('//*') AS inp(nod)

You get an output like this:

record
field
id
id
field
info

Answer 3

Instead of those attempts with name() or local-name() I would use self::id e.g.

if ($i[self::id]) then ... else ...

Answer 4

Another neat XQuery solution is to use typeswitch:

for $i in $records/record/field | $records/record/id
return
  typeswitch($i)
  case element(id) return ...
  case element(field) return ...
  default return ...

Answer 5

How about something simpler and more XQuery-like

for $i in $records/record/field return do something with field,
for $i in $records/record/id return do something with id

In this case, the values returned by the first for will be merged with the values from the 2nd for.

Answer 6

Use typeswitch:

let $record :=
<record>
  <field name="f1"/>
  <id name="f2"/>
  <id name="f3"/>
  <field name="f4"/>
  <info/>
</record>

for $e in $record/*
return
  typeswitch ($e) 
    case element(id) return concat("id",$e/@name)
    case element (field) return concat("field",$e/@name)
    default return "other"