Share via

  • Article

Using Abbreviated Syntax in a Path Expression

All the examples in Understanding the Path Expressions in XQuery use unabbreviated syntax for path expressions. The unabbreviated syntax for an axis step in a path expression includes the axis name and node test, separated by double colon, and followed by zero or more step qualifiers.

For example:

child::ProductDescription[attribute::ProductModelID=19]

XQuery supports the following abbreviations for use in path expressions:

  • The child axis is the default axis. Therefore, the child:: axis can be omitted from a step in an expression. For example, /child::ProductDescription/child::Summary can be written as /ProductDescription/Summary.

  • An attribute axis can be abbreviated as @. For example, /child::ProductDescription[attribute::ProductModelID=10] can be written as /ProudctDescription[@ProductModelID=10].

  • A /descendant-or-self::node()/ can be abbreviated as //. For example, /descendant-or-self::node()/child::act:telephoneNumber can be written as //act:telephoneNumber.

    The previous query retrieves all telephone numbers stored in the AdditionalContactInfo column in the Contact table. The schema for AdditionalContactInfo is defined in a way that a <telephoneNumber> element can appear anywhere in the document. Therefore, to retrieve all the telephone numbers, you must search every node in the document. The search starts at the root of the document and continues through all the descendant nodes.

    The following query retrieves all the telephone numbers for a specific customer contact:

     SELECT AdditionalContactInfo.query('           
             declare namespace act="https://schemas.microsoft.com/sqlserver/2004/07/adventure-works/ContactTypes";           
             declare namespace crm="http://schemas.adventure-works.com/Contact/Record";           
             declare namespace ci="https://schemas.microsoft.com/sqlserver/2004/07/adventure-works/ContactInfo";           
             /descendant-or-self::node()/child::act:telephoneNumber           
             ') as result           
 FROM Person.Person           
 WHERE BusinessEntityID = 291;

    If you replace the path expression with the abbreviated syntax, //act:telephoneNumber, you receive the same results.

  • The self::node() in a step can be abbreviated to a single dot (.). However, the dot is not equivalent or interchangeable with the self::node().

    For example, in the following query, the use of a dot represents a value and not a node:

    ("abc", "cde")[. > "b"]

  • The parent::node() in a step can be abbreviated to a double dot (..).