Filter expressions

A filter expression consists of a primary expression that is followed by zero or more predicates. The predicates, if present, filter the result of the primary expression.

The result of a filter expression consists of all the items that are returned by the primary expression for which all the predicates are true. If no predicates are specified, the result is the result of the primary expression. This result can contain nodes, atomic values, or a combination of nodes and atomic values. The ordering of the items that are returned by a filter expression is the same as their order in the result of the primary expression. Context positions are assigned to items based on their ordinal position in the result sequence. The first context position is 1.

Restriction: An XPath step node or XPath predicate cannot contain FLWOR expressions, conditional expressions, or comma operators.

Syntax

filter-expression
Read syntax diagramSkip visual syntax diagramprimary-expressionpredicate-list
predicate-list
Read syntax diagramSkip visual syntax diagram[expression]

Examples

The following example uses a filter expression that returns a value if there is a customerinfo element anywhere in the document that is specified by $x:
SELECT XMLQUERY ('declare default element namespace "http://posample.org";
  $x[.//customerinfo]'
  PASSING PASSING INFO AS "x")
FROM CUSTOMER