RE: Anyone can explain me this syntax?

Hi,

> From Muenchian method of grouping, I always use something like this:
> 
> ROW[count(. | key('relacion_x_cobertura', REL_ID)[1]) = 1]

  key('relacion_x_cobertura', REL_ID)

will return a node-set whose "relacion_x_cobertura" key value is the same as the string value of REL_ID element,
 
  key('relacion_x_cobertura', REL_ID)[1]

of that node-set, select the first,

  . | key('relacion_x_cobertura', REL_ID)[1]

create an union of that node-set with the current node. Remember that a node-set will *not* contain dublicates, so if the current node is same node as the first one returned by the key, the resulting set will only contain the current node.

  count(. | key('relacion_x_cobertura', REL_ID)[1])

count the number of nodes in the union set,

  count(. | key('relacion_x_cobertura', REL_ID)[1]) = 1

and if the count is equal to one, return boolean true. In effect, check if the current node is the same node as the first one returned by the key.

> - Why the . (dot) is used? why if I omit it, it doesn't work 
> (it returns all elements)?

The current node. See <http://www.w3.org/TR/xpath#NT-AbbreviatedStep>.

> - What's the meaning of the | (pipe)?

You haven't read the XPath 1.0 spec, have you? See <http://www.w3.org/TR/xpath#NT-UnionExpr>.

> - What's the meaning of [1]? I have always used things like 
> [FIELD_NAME=some_value]. I understand that perfectly, but 
> what about placing only that number in the brackets? I tried 
> by using [2] and it worked too... or, perhaps I was lucky?

Read the XPath 1.0 spec, you'll feel better in the morning.

Cheers,

Jarno

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