Constructors

Direct constructors use an XML-like notation to create XML structures within a query. XQuery provides direct constructors for creating element nodes (which might include attribute nodes, text nodes, and nested element nodes), processing instruction nodes, and comment nodes. For example, the following constructor creates a book element that contains an attribute and some nested elements:

<book isbn="isbn-0060229357">
  <title>Harold and the Purple Crayon</title>
  <author>
    <first>Crockett</first>
    <last>Johnson</last>
  </author>
</book>

Computed constructors use a notation that is based on enclosed expressions to create XML structures within a query. A computed constructor begins with a keyword that identifies the type of node to be created and is followed by the name of the node, if applicable, and an enclosed expression that computes the content of the node. XQuery provides computed constructors for creating element nodes, attribute nodes, document nodes, text nodes, processing-instruction nodes, and comment nodes. For example, the following query contains computed constructors that generate the same result as the direct constructor described in the previous example:

element book {
  attribute isbn {"isbn-0060229357" },
  element title { "Harold and the Purple Crayon"},
  element author {
    element first { "Crockett" },
    element last {"Johnson" }
  }
}