Description
The fn:zero-or-one function returns $arg if it contains zero or one items. Otherwise, the error FORG0003 is raised. This function is useful when static typing is in effect, to avoid apparent static type errors.
This description is © Copyright 2007, Priscilla Walmsley. It is excerpted from the book XQuery by Priscilla Walmsley, O'Reilly, 2007. For a complete explanation of this function, please refer to Appendix A of the book. Arguments and Return TypeName | Type |
$arg |
item()* |
return value |
item()? |
ExamplesXQuery Example | Results |
---|
zero-or-one( () ) |
() |
zero-or-one('a') |
a |
zero-or-one( ('a', 'b') ) |
Error FORG0003 |
See Alsofn:one-or-more | Returns a sequence if it contains one or more items, otherwise errors | fn:exactly-one | Returns a sequence if it contains exactly one item, otherwise errors |
History |
Recommended Reading:
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